Hydraulic Control Apparatus and Brake System

ABSTRACT

An object of the present invention is to provide a hydraulic control apparatus capable of further effectively preventing or reducing a vibration. A second unit includes a housing including fluid passages and the like provided therein and configured to be mounted on a vehicle, a rotational driving shaft provided inside the housing, and a plurality of pump portions configured to be activated by a rotation of the rotational driving shaft and disposed in a direction around a central axis of the rotational driving shaft inside the housing. The pump portions are provided in such a manner that the number of pump portions positioned on a vertically lower side is larger than the number of pump portions positioned on a vertically upper side with respect to the central axis of the rotational driving shaft with the housing mounted on the vehicle.

TECHNICAL FIELD

The present invention relates to a hydraulic control apparatus.

BACKGROUND ART

Conventionally, there has been known a hydraulic control apparatusincluding a plurality of plunger pumps (for example, PTL 1).

CITATION LIST Patent Literature

PTL 1: US Patent Application Public Disclosure No. 2013/0145758

SUMMARY OF INVENTION Technical Problem

One of objects of the present invention is to provide a hydrauliccontrol apparatus capable of further effectively damping a vibration.

Solution to Problem

According to one aspect of the present invention, a hydraulic controlapparatus is configured in such a manner that the number of plungerpumps positioned on a vertically lower side is larger than the number ofplunger pumps positioned on a vertically upper side with respect to acentral axis of a rotational driving shaft in a state mounted on avehicle.

Therefore, the hydraulic control apparatus according to the one aspectof the present invention can further effectively damp the vibration.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view of a part of a brake system according to afirst embodiment.

FIG. 2 illustrates a schematic configuration of the brake systemaccording to the first embodiment.

FIG. 3 is a perspective view of a second unit according to the firstembodiment.

FIG. 4 is a front view of the second unit according to the firstembodiment.

FIG. 5 is a side view of the second unit according to the firstembodiment.

FIG. 6 is a top view of the second unit according to the firstembodiment.

FIG. 7 is a cross-sectional view taken along a line VII-VII illustratedin FIG. 6.

FIG. 8 is a perspective view of the second unit with a pin or the likeattached thereto according to the first embodiment.

FIG. 9 is a perspective view of the second unit set on a mount accordingto the first embodiment.

FIG. 10 is a front view (a cross-sectional view) of the second unit seton the mount according to the first embodiment.

FIG. 11 is a cross-sectional view taken along a line XI-XI illustratedin FIG. 10.

FIG. 12 is an exploded perspective view illustrating a process ofattaching the second unit onto the mount according to the firstembodiment.

FIG. 13 is a perspective view of a second unit with the pin and the likeattached thereto according to a second embodiment.

FIG. 14 is a perspective view of the second unit set on the mountaccording to the second embodiment.

FIG. 15 is a front view (a cross-sectional view) of the second unit seton the mount according to the second embodiment.

FIG. 16 is an exploded perspective view illustrating a process ofattaching the second unit onto the mount according to the secondembodiment.

DESCRIPTION OF EMBODIMENTS

In the following description, embodiments for implementing the presentinvention will be described with reference to the drawings.

First Embodiment

First, a configuration will be described. FIG. 1 illustrates an outerappearance of a part of a brake system 1 according to the presentembodiment from an angle. FIG. 2 illustrates a schematic configurationof the brake system 1 together with a hydraulic circuit, and illustratesa cross section of a first unit 1A. The brake system 1 is usable for ahybrid automobile including an electric motor (a generator) in additionto an internal combustion engine, an electric automobile including onlythe electric motor, and the like, besides a general vehicle includingonly the internal combustion engine (an engine) as a prime mover thatdrives wheels. The brake system 1 is a hydraulic braking apparatus thatprovides a frictional braking force with use of a hydraulic pressure toeach of wheels FL to RR of the vehicle. A brake actuation unit isprovided on each of the wheels FL to RR. The brake actuation unit is,for example, a disk-type brake, and includes a wheel cylinder W/C and acaliper. The caliper includes a brake disk and brake pads. The brakedisk is a brake rotor rotatable integrally with a tire. The brake padsare disposed with a predetermined clearance generated from the brakedisk, and contact the brake disk by being moved by a hydraulic pressurein the wheel cylinder W/C. By this operation, the brake actuation unitgenerates the frictional braking force. The brake system 1 includes twobrake pipes (a primary P system and a secondary S system). A brake pipeconfiguration is, for example, an X-split pipe configuration. The brakesystem 1 may employ another piping method, such as a front/rear splitpipe configuration. Hereinafter, when a member provided incorrespondence with the P system and a member provided in correspondencewith the S system should be distinguished from each other, indices P andS will be added at the ends of the respective reference numerals. Thebrake system 1 supplies brake fluid as hydraulic fluid (hydraulicliquid) to each of the brake actuation units via a brake pipe, andgenerates the hydraulic pressure (a brake hydraulic pressure) in thewheel cylinder W/C. By this operation, the brake system 1 provides thehydraulic braking force to each of the wheels FL to RR.

The brake system 1 includes the first unit 1A and a second unit 1B. Thewheel cylinder W/C on each of the wheels FL to RR and the second unit 1Bare connected to each other via a wheel cylinder pipe 10W. The firstunit 1A and the second unit 1B are set up in, for example, an engineroom isolated from a driving compartment of the vehicle, and areconnected to each other via a plurality of pipes. The plurality of pipesinclude master cylinder pipes 10M (a primary pipe 10MP and a secondarypipe 10MS), an intake pipe 10R, and a backpressure pipe 10X. Except forthe intake pipe 10R, each of the pipes 10M, 10W, and 10X is a metallicbrake pipe (a metallic pipe), and, in particular, a steel tube such as adouble walled steel tube. Both ends of each of the pipes 10M, 10W, and10X each include a male pipe joint processed by flared processing. Theintake pipe 10R is a brake hose (a hose pipe) formed so as to becomeflexible from a material such as rubber. Ends of the intake pipe 10R areconnected to a port 873 and the like via nipples 10R1 and 10R2. Thenipples 10R1 and 10R2 are each a resin connection member having atubular portion. Hereinafter, a three-dimensional orthogonal coordinatesystem having an X axis, a Y axis, and a Z axis is set for convenienceof the description. A Z-axis direction is defined to be a verticaldirection and a Z-axis positive direction side is defined to be an upperside in the vertical direction with the first unit 1A and the secondunit 1B mounted on the vehicle. An X-axis direction is defined to be alongitudinal direction of the vehicle and an X-axis positive directionside is defined to be a front side of the vehicle. A Y-axis direction isdefined to be a lateral direction of the vehicle.

A brake pedal 100 is a brake operation member that receives an input ofa brake operation performed by an operator (a driver). A push rod PR isrotatably connected to the brake pedal 100. The push rod PR extends froman end on an X-axis negative direction side that is connected to thebrake pedal 100 toward the X-axis positive direction side. The firstunit 1A is a brake operation unit mechanically connected to the brakepedal 100, and is a master cylinder unit including a master cylinder 5.The first unit 1A includes a reservoir tank 4, a housing 7, the mastercylinder 5, a stroke sensor 94, and a stroke simulator 6. The reservoirtank 4 is a brake fluid source storing the brake fluid therein, and is alow-pressure portion opened to an atmospheric pressure. Replenishmentports 40P and 40S, a supply port 41, a first partition wall 421, and asecond partition wall 422 are provided in the reservoir tank 4. Thepartition walls 421 and 422 extend from a bottom portion of thereservoir tank 4 to a predetermined height, and partition a bottomportion side of the reservoir tank 4 into three chambers 43. The threechambers 43 include first chambers 43P and 43S, and a second chamber43R. The replenishment ports 40P and 40S are opened to the firstchambers 43P and 43S, respectively, and the supply port 41 is opened tothe second chamber 43R. One end of the intake pipe 10R is connected tothe supply port 41. The housing 7 contains (houses) the master cylinder5 and the stroke simulator 6 therein. A rectangular plate-like flangeportion 78 is provided at an end of the housing 7 on the X-axis negativedirection side. Four corners of the flange portion 78 are fixed to adash panel on a vehicle body side with use of bolts B1. The reservoirtank 4 is set on a Z-axis positive direction side of the housing 7.

A cylinder 70 for the master cylinder 5, a cylinder 71 for the strokesimulator 6, and a plurality of fluid passages (fluid passages) areformed inside the housing 7. The cylinder 70 for the master cylinder 5has a bottomed cylindrical shape extending in the X-axis direction, andis closed and opened on an X-axis positive direction side and an X-axisnegative direction side thereof, respectively. The cylinder 70 includesa small-diameter portion 701 and a large-diameter portion 702 on theX-axis positive direction side and the X-axis negative direction sidethereof, respectively. The small-diameter portion 701 includes two sealgrooves 703 and 704 and one port 705 for each of the P system and the Ssystem. The seal grooves 703 and 704 and the port 705 each have anannular shape extending in a direction around a central axis of thecylinder 70. The port 705 is disposed between the two seal grooves 703and 704. The cylinder 71 for the stroke simulator 6 is disposed on aZ-axis negative direction side of the cylinder 70. The cylinder 71 has abottomed cylindrical shape extending in the X-axis direction, and isclosed and opened on an X-axis positive direction side and an X-axisnegative direction side thereof, respectively. The cylinder 71 includesa small-diameter portion 711 and a large-diameter portion 712 on theX-axis positive direction side and the X-axis negative direction sidethereof, respectively. A first seal groove 713 and a second seal groove714 are provided on an inner peripheral surface of the small-diameterportion 711 at a generally central position in the X-axis direction andan X-axis negative direction side thereof, respectively. The sealgrooves 713 and 714 each have an annular shape extending in a directionaround a central axis of the cylinder 71.

The plurality of fluid passages includes replenishment fluid passages72, supply fluid passages 73, and a positive pressure fluid passage 74.A plurality of ports is formed inside the housing 7, and these ports areopened on an outer surface of the housing 7. The plurality of portsincludes replenishment ports 75, supply ports 76, and a backpressureport 77. The replenishment fluid passages 72P and 72S extend from thereplenishment ports 75P and 75S to be opened to the ports 705P and 705S,respectively. The supply fluid passages 73P and 76S extend from thesmall-diameter portion 701 of the cylinder 70 to be opened to the supplyports 76P and 76S, respectively. The positive pressure fluid passage 74extends from an end of the small-diameter portion 711 in the X-axispositive direction to be connected to the supply fluid passage 73S. Thereplenishment ports 75P and 75S are connected to the replenishment ports40P and 40S of the reservoir tank 4, respectively. One end of theprimary pipe 10MP is connected to the supply port 76P. One end of thesecondary pipe 10MS is connected to the supply port 76S. One end of thebackpressure pipe 10X is connected to the backpressure port 77. Morespecifically, the pipe joint at the end of the primary pipe 10MP isfastened and fixed by being fitted in the supply port 76P and sandwichedbetween the supply port 76P and the housing 7 by a nut, by which theabove-described end is connected to the supply port 76P. The oppositeend of the primary pipe 10MP and both ends of the other metallic pipes10MS, 10W, and 10X are also connected to the ports in a similar manner.

The master cylinder 5 is a first hydraulic source capable of supplyingthe hydraulic pressure to the wheel cylinder W/C, and is connected tothe brake pedal 100 via the push rod RP and actuated according to anoperation performed by the driver on the brake pedal 100. The mastercylinder 5 includes pistons 51 axially movable according to theoperation on the brake pedal 100. The pistons 51 are contained in thecylinder 70 and define hydraulic chambers 50. The master cylinder 5 is atandem-type cylinder, and includes a primary piston 51P connected to thepush rod RP and a secondary piston 51S configured as a free piston inseries as the pistons 51. The stroke sensor 94 includes a magnet 940 anda sensor main body 941 (a Hall element or the like). The magnet 940 isprovided on the primary piston 51P, and the sensor main body 941 isattached on the outer surface of the housing 7. The pistons 51P and 51Seach have a bottomed cylindrical shape, and are movable in the X-axisdirection along the inner peripheral surface of the small-diameterportion 701. The pistons 51 each include a first recessed portion 511and a second recessed portion 512 sharing a common bottom portion formedby a partition wall 510. A hole 513 penetrates through a circumferentialwall of the first recessed portion 511. The first recessed portion 511is disposed on the X-axis positive direction side, and the secondrecessed portion 512 is disposed on the X-axis negative direction side.An X-axis positive direction side of the push rod RP is contained in thesecond recessed portion 512P of the primary piston 51P. Asemi-spherically rounded end of the push rod RP in the X-axis positivedirection is in abutment with the partition wall 510P. A flange portionPR1 is provided on the push rod PR. A movement of the push rod RP towardthe X-axis negative direction side is regulated by abutment between astopper portion 700 provided at an opening portion of the cylinder 70(the large-diameter portion 702) and the flange portion PR1. In thesmall-diameter portion 701, a primary chamber 50P is defined between theprimary piston 51P (the first recessed portion 511P) and the secondarypiston 51S (the second recessed portion 512S), and a secondary chamber50S is defined between the secondary piston 51S (the first recessedportion 5115) and an end of the small-diameter portion 701 in the X-axispositive direction. The supply fluid passages 73P and 73S are constantlyopened to the individual chambers 50P and 50S, respectively.

A spring 52P, a first retainer member 54A, a second retainer member 54B,and a stopper member 55 are set in the primary chamber 50P. The retainermembers 54 each include a cylindrical portion 540. A first flangeportion 541 flares radially outwardly on one axial end side of thecylindrical portion 540, and a second flange portion 542 flares radiallyinwardly on an opposite axial end side of the cylindrical portion 540.The first flange portion 541 of the first retainer member 54A is set onthe partition wall 510S, and the first flange portion 541 of the secondretainer member 54B is set on the partition wall 510P. The stoppermember 55 has a bolt-like shape including a shaft portion 550, and ahead portion 551 thereof flares radially outwardly at an end of theshaft portion 550. An opposite end of the shaft portion 550 is fixed tothe second flange portion 542 of the second retainer member 54B. Thehead portion 551 is contained on an inner peripheral side of thecylindrical portion 540 of the first retainer member 54A movably alongan inner peripheral surface of the cylindrical portion 540. Detachmentof the head portion 551 from the cylindrical portion 540 is regulated byabutment of the head portion 551 against the second flange portion 542.The spring 52P is a coil spring as an elastic member, and a returnspring constantly biasing the primary piston 51P toward the X-axisnegative direction side. An X-axis positive direction side of the spring52P is fitted to the cylindrical portion 540 of the first retainermember 54A and held by the first retainer member 54A. An X-axis negativedirection side of the spring 52P is fitted to the cylindrical portion540 of the second retainer member 54B and held by the second retainermember 54B. The spring 52P is set in a pressed and compressed statebetween the first flange portion 541 of the first retainer member 54A(the partition wall 510S) and the first flange portion 541 of the secondretainer member 54B (the partition wall 510P). A spring 52S, the firstretainer member 54A, the second retainer member 54B, and the stoppermember 55 are set in the secondary chamber 50S. The first flange portion541 of the first retainer member 54A is set at an end of thesmall-diameter portion 701 in the X-axis positive direction, and thefirst flange portion 541 of the second retainer member 54B is set on thepartition wall 510S. The spring 52S is an elastic member as a returnspring constantly biasing the secondary piston 51S toward the X-axisnegative direction side. The spring 52S is set in a pressed andcompressed state between the first flange portion 541 of the firstretainer member 54A (the end of the small-diameter portion 701 in theX-axis positive direction) and the first flange portion 541 of thesecond retainer member 54B (the partition wall 510S). A layout andconfiguration of the stopper member 55 and the like other than that aresimilar to the primary chamber 50P side.

Cup-like seal members 531 and 532 are set in the seal grooves 703 and704, respectively. Lip portions of the seal members 531 and 532 are insliding contact with outer peripheral surfaces of the pistons 51. Theseal member 531P on the X-axis negative direction side on the primaryside prevents or reduces a flow of the brake fluid directed from theX-axis positive direction side (the port 705P) toward the X-axisnegative direction side (the large-diameter portion 702). The sealmember 532P on the X-axis positive direction side prevents or reduces aflow of the brake fluid directed toward the X-axis negative directionside (the port 705P), and permits a flow of the brake fluid directedtoward the X-axis positive direction side (the primary chamber 50P). Theseal member 531S on the X-axis negative direction side on the secondaryside prevents or reduces a flow of the brake fluid directed from theX-axis negative direction side (the primary chamber 50P) toward theX-axis positive direction side (the port 705S). The seal member 532S onthe X-axis positive direction side prevents or reduces a flow of thebrake fluid directed toward the X-axis negative direction side (the port705S), and permits a flow of the brake fluid directed toward the X-axispositive direction side (the secondary chamber 50S). The holes 513 areeach positioned between portions where both the seal members 531 and 532(the lip portions) and the outer peripheral surface of the piston 51 arein contact with each other (one side closer to the seal member 532 onthe X-axis positive direction side) in an initial state, in which boththe pistons 51P and 51S are maximally displaced toward the X-axisnegative direction side.

The stroke simulator 6 is activated according to the brake operationperformed by the driver, and provides a reaction force and a stroke tothe brake pedal 100. The stroke simulator 6 includes a piston 61, afirst seal member 621, a second seal member 622, a first retainer member64A, a second retainer member 64B, a third retainer member 66, a stoppermember 65, a plug member 67, a first spring 681, a second spring 682, afirst damper 691, and a second damper 692. The piston 61 has a bottomedcylindrical shape and is contained in the cylinder 71. The piston 61includes a first recessed portion 611 opened on the X-axis positivedirection side and a second recessed portion 612 opened on the X-axisnegative direction side. A columnar protruding portion 613 is providedinside the second recessed portion 612. The protruding portion 613protrudes from a wall portion 610 separating the first and secondrecessed portions 611 and 612 therebetween. The piston 61 is movable inthe X-axis direction along the inner peripheral surface of thesmall-diameter portion 711. An inside of the cylinder 71 is partitionedand divided into two chambers by the piston 61. A positive pressurechamber 601 (a main chamber) as a first chamber is defined between anX-axis positive direction side (including an inner peripheral side ofthe first recessed portion 611) of the piston 61 and the small-diameterportion 711. A backpressure chamber 602 (a sub chamber) as a secondchamber is defined between an X-axis negative direction side of thepiston 61 and the large-diameter portion 712. Cup-like first and secondseal members 621 and 622 are set in the first and second seal grooves713 and 714, respectively. Lip portions of the seal members 621 and 622are in sliding contact with an outer peripheral surface of the piston61. The first seal member 621 prevents or reduces a flow of the brakefluid directed from the X-axis positive direction side (the positivepressure chamber 601) toward the X-axis negative direction side (thebackpressure chamber 602). The second seal member 622 prevents orreduces a flow of the brake fluid directed from the X-axis negativedirection side (the backpressure chamber 602) toward the X-axis positivedirection side (the positive pressure chamber 601). The positivepressure chamber 601 and the backpressure chamber 602 are liquid-tightlyseparated from each other by the seal members 621 and 622. Each of theseal members 621 and 622 may be an X-ring, or may be configured in sucha manner that two cup-like seal members are arranged and disposed so asto be able to prevent or reduce the flows of the brake fluid to both thepositive pressure chamber 601 and the backpressure chamber 602. Further,in the present embodiment, the seal grooves 713 and 714 are provided tothe small-diameter portion 711 of the cylinder 71 as a structure forsetting the seal members 621 and 622 (the seal members 621 and 622 areconfigured as so-called rod seals), but the seal grooves may be insteadprovided to the piston 61 (the seal members 621 and 622 may beconfigured so-called piston seals).

The retainer members 64 and 66, the stopper member 65, the springs 681and 682, and the dampers 691 and 692 are contained in the backpressurechamber 602. The third retainer member 66 has a bottomed cylindricalshape including a cylindrical portion 660 and a bottom portion 661, anda flange portion 662 flares radially outwardly on an opening side of thecylindrical portion 660. The first damper 691 is an elastic member suchas rubber, and has a columnar shape. The second damper 692 is an elasticmember such as rubber, and has a columnar shape narrowed at an axiallycentral portion thereof. A plug member 67 closes the opening of thecylinder (the large-diameter portion 712). A bottomed cylindrical firstrecessed portion 671 and a bottomed annular second recessed portion 672are provided on an X-axis positive direction side of the plug member 67.The second damper 692 is set in the first recessed portion 671. Oneaxial end side of a cylindrical portion 640 of the first retainer member64A is fitted to the protruding portion 613 of the piston 61. The firstdamper 691 is set in abutment with the protruding portion 613 on aninner peripheral side of the cylindrical portion 630. The secondretainer member 64B is set on an inner peripheral side of the thirdretainer member 66 (the cylindrical portion 660) in such a manner that aflange portion 641 is brought into abutment with the bottom portion 641.The first and second springs 681 and 682 are each an elastic member as areturn spring constantly biasing the piston 61 toward one side where thepositive pressure chamber 601 is located (a direction for reducing avolume of the positive pressure chamber 601 and increasing a volume ofthe backpressure chamber 602). The first spring 681 is a coil springsmall in diameter. The first spring 681 is set in a pressed andcompressed state between an end surface of the piston 61 in the X-axisnegative direction (the first flange portion 641 of the first retainermember 64A) and the first flange portion 641 of the second retainermember 64B (the bottom portion 661 of the third retainer member 66). Thesecond spring 682 is a coil spring large in diameter that has a largerspring coefficient than the first spring 681. An X-axis positivedirection side of the second spring 682 is fitted to the cylindricalportion 660 of the third retainer member 66 and held by the thirdretainer member 66. An X-axis negative direction side of the secondspring 682 is contained in the second recessed portion 672 of the plugmember 67 and held by the plug member 67. The second spring 682 is setin a pressed and compressed state between the flange portion 662 of thethird retainer member 66 and the plug member 67 (a bottom portion of thesecond recessed portion 672.) A layout configuration of the stoppermember 65 and the like other than that is similar to the hydraulicchamber 50 of the master cylinder 5.

The second unit 1B is a hydraulic control apparatus provided between thefirst unit 1A and the brake actuation unit of each of the wheels FL toRR. FIGS. 3 to 6 illustrate an outer appearance of the second unit 1B.FIG. 3 is a perspective view of the second unit 1B as viewed from theX-axis positive direction side, the Y-axis positive direction side, andthe Z-axis positive direction side. FIG. 4 is a front view of the secondunit 1B as viewed from the Y-axis positive direction side. FIG. 5 is aright side view of the second unit 1B as viewed from the X-axis positivedirection side. FIG. 6 is a top view of the second unit 1B as viewedfrom the Z-axis positive direction side. FIG. 7 illustrates a crosssection taken along a line VII-VII in FIG. 6. The second unit 1Bincludes a housing 8, a motor 20, a pump 3, a plurality ofelectromagnetic valves 21 and the like, a plurality of hydraulic sensors91 and the like, and an electronic control unit (a control unit,hereinafter referred to as an ECU) 90. The housing 8 contains (houses)the pump 3 and valve bodies of the electromagnetic valves 21 and thelike therein. Circuits (brake hydraulic circuits) of the above-describedtwo systems (the P system and the S system), through which the brakefluid flows, are formed by plurality of fluid passages inside thehousing 8. The plurality of fluid passages includes supply fluidpassages 11, an intake fluid passage 12, a discharge fluid passage 13, apressure adjustment fluid passage 14, a pressure reduction fluid passage15, a backpressure fluid passage 16, a first simulator fluid passage 17,and a second simulator fluid passage 18. Further, a plurality of ports87 is formed inside the housing 8, and these ports 87 are opened on anouter surface of the housing 8. The plurality of ports 87 are connectedto the fluid passages inside the housing 8, and connects these internalfluid passages and the fluid passages (the pipe 10M and the like)outside the housing 8 to each other. The plurality of ports 87 includesmaster cylinder ports 871 (a primary port 871P and a secondary port871S), an intake port 873, a backpressure port 874, and wheel cylinderports 872. The master cylinder ports 871 are connected to the supplyfluid passages 11 inside the housing 8, and also connect the housing 8(the second unit 1B) to the master cylinder 5 (the hydraulic chamber50). An opposite end of the primary pipe 10MP is connected to theprimary port 871P. An opposite end of the secondary pipe 10MS isconnected to the secondary port 871S. The intake port 873 is connectedto a first fluid pool chamber 83 inside the housing 8, and also connectsthe housing 8 to the reservoir tank 4 (the second chamber 43R). Thenipple 10R2 is fixedly set in the intake port 873, and an opposite endof the intake pipe 10R is connected to the nipple 10R2. The backpressureport 874 is connected to the backpressure fluid passage 16 inside thehousing, and also connects the housing 8 to the stroke simulator 6 (thebackpressure chamber 602). An opposite end of the backpressure pipe 10Xis connected to the backpressure port 874. The wheel cylinder ports 872are connected to the supply fluid passages 11 inside the housing 8, andalso connect the housing 8 (the second unit 1B) to the wheel cylindersW/C. One end of each of the wheel cylinder pipes 10W is connected to thewheel cylinder port 872.

The motor 20 is a rotary electric motor, and includes a rotational shaftfor driving the pump 3. The motor 20 may be a brushed motor or may be abrushless motor including a resolver that detects a rotational angle orthe number of rotations of the rotational shaft. The pump 3 is a secondhydraulic source capable of supplying the hydraulic pressure to thewheel cylinder W/C, and includes five pump portions 3A to 3E configuredto be driven by one motor 20. The pump 3 is used by the S system and theP system in common. The electromagnetic valves 21 and the like are eachan actuator that operates according to a control signal, and eachinclude a solenoid and a valve body. The valve body is stroked accordingto power supply to the solenoid to switch opening/closing of the fluidpassage (establishes or blocks communication through the fluid passage).The electromagnetic valves 21 and the like each generate a controlhydraulic pressure by controlling a communication state of theabove-described circuit to adjust a flow state of the brake fluid. Theplurality of electromagnetic valves 21 and the like include shut-offvalves 21, pressure increase valves (hereinafter referred to as SOL/VINs) 22, communication valves 23, a pressure adjustment valve 24,pressure reduction valves (hereinafter referred to as SOL/V OUTs) 25, astroke simulator IN valve (hereinafter referred to as an SS/V IN) 27,and a stroke simulator OUT valve (hereinafter referred to as an SS/VOUT) 28. The shut-off valves 21, the SOL/V INs 22, and the pressureadjustment valve 24 are each a normally opened valve opened when nopower is supplied thereto. The communication valves 23, the pressurereduction valves 25, the SS/V IN 27, and the SS/V OUT 28 are each anormally closed valve closed when no power is supplied thereto. Theshut-off valves 21, the SOL/V INs 22, and the pressure control valve 24are each a proportional control valve, an opening degree of which isadjusted according to a current supplied to the solenoid. Thecommunication valves 23, the pressure reduction valves 25, the SS/V IN27, and the SS/V OUT 28 are each an ON/OFF valve, opening/closing ofwhich is controlled to be switched between two values, i.e., switched tobe either opened or closed. The proportional control valve can also beused as these valves. The hydraulic sensor 91 and the like detect adischarge pressure of the pump 3 and a master cylinder pressure. Theplurality of hydraulic sensors includes a master cylinder pressuresensor 91, a discharge pressure sensor 93, and wheel cylinder pressuresensors 92 (a primary pressure sensor 92P and a secondary pressuresensor 92S).

In the following description, the brake hydraulic circuit of the secondunit 1B will be described with reference to FIG. 2. Memberscorresponding to the individual wheels FL to RR will be distinguishedfrom one another if necessary, by indices a to d added at the ends ofreference numerals thereof, respectively. One end side of the supplyfluid passage 11P is connected to the primary port 871P. An opposite endside of the fluid passage 11P branches off into a fluid passage 11 a forthe front left wheel and a fluid passage 11D for a rear right wheel 11d. Each of the fluid passages 11 a and 11 d are connected to the wheelcylinder port 872 corresponding thereto. One end side of the supplyfluid passage 11S is connected to the secondary port 871S. An oppositeend side of the fluid passage 11S branches off into a fluid passage 11 bfor the front right wheel and a fluid passage 11 c for the rear leftwheel. Each of the fluid passages 11 b and 11 c is connected to thewheel cylinder port 872 corresponding thereto. The shut-off valves 21are provided on the above-described one end sides of the fluid passages11. The SOL/V IN 22 is provided in each of the fluid passages 11 a to 11d on the above-described opposite end side. A bypass fluid passage 110is provided in parallel with each of the fluid passages 11 whilebypassing the SOL/V IN 22, and a check valve 220 is provided in thefluid passage 110. The valve 220 permits only a flow of the brake fluiddirected from one side where the wheel cylinder port 872 is locatedtoward the other side where the master cylinder port 871 is located.

The intake fluid passage 12 connects the first fluid pool chamber 83 andan intake port 823 of the pump 3 to each other. One end side of thedischarge fluid passage 13 is connected to a discharge port 821 of thepump 3. An opposite end side of the discharge fluid passage 13 branchesoff into a fluid passage 13P for the P system and a fluid passage 13Sfor the S system. Each of the fluid passages 13P and 13S are connectedto portions of the supply fluid passages 11 between the shut-off valves21 and the SOL/V INs 22. The communication valve 23 is provided in eachof the fluid passages 13P and 13S. Each of the fluid passages 13P and13S functions as a communication passage connecting the supply fluidpassage 11P of the P system and the supply fluid passage 11S of the Ssystem to each other. The pump 3 is connected to each of the wheelcylinder ports 872 via the above-described communication passages (thedischarge fluid passages 13P and 13S) and the supply fluid passages 11Pand 11S. The pressure reduction fluid passage 14 connects a portion ofthe discharge fluid passage 13 between the pump 3 and the communicationvalves 23, and the first fluid pool chamber 83 to each other. Thepressure adjustment valve 24 as a first pressure reduction valve isprovided in the fluid passage 14. The pressure reduction fluid passage15 connects a portion of each of the fluid passages 11 a to 11 d of thesupply fluid passages 11 between the SOL/V IN 22 and the wheel cylinderport 872, and the first fluid pool chamber 83 to each other. The SOL/VOUTs 25 as second pressure reduction valves are provided in the fluidpassages 15.

One end side of the backpressure chamber 16 is connected to thebackpressure port 874. An opposite end side of the fluid passage 16branches off into the first simulator fluid passage 17 and the secondsimulator fluid passage 18. The first simulator fluid passage 17 isconnected to a portion of the supply fluid passage 11S between theshut-off valve 21S and the SOL/V INs 22 b and 22 c. The SS/V IN 27 isprovided in the fluid passage 17. A bypass fluid passage 170 is providedin parallel with the fluid passage 17 while bypassing the SS/V IN 27,and a check valve 270 is provided in the fluid passage 170. The valve270 permits only a flow of the brake fluid directed from one side wherethe backpressure fluid passage 16 is located toward the other side wherethe supply fluid passage 11S is located. The second simulator fluidpassage 18 is connected to the first fluid pool chamber 83. The SS/V OUT28 is provided in the fluid passage 18. A bypass fluid passage 180 isprovided in parallel with the fluid passage 18 while bypassing the SS/VOUT 28, and a check valve 280 is provided in the fluid passage 180. Thevalve 280 permits only a flow of the brake fluid directed from one sidewhere the first fluid pool chamber 83 is located toward the other sidewhere the backpressure fluid passage 16 is located. The hydraulic sensor91 is provided between the shut-off valve 21S and the secondary port871S in the supply fluid passage 11S. The hydraulic sensor 91 detects ahydraulic pressure at this portion (a hydraulic pressure in the positivepressure chamber 601 of the stroke simulator 6, and the master cylinderpressure). The hydraulic sensors 92 are provided between the shut-offvalves 21 and the SOL/V INs 22 in the supply fluid passages 11. Thehydraulic sensors 92 detects hydraulic pressures at these portions(corresponding to the wheel cylinder hydraulic pressures). The hydraulicsensor 93 is provided between the pump 3 and the communication valves 23in the discharge fluid passage 13. The hydraulic sensor 93 detects ahydraulic pressure at this portion (the pump discharge pressure).

Each of the hydraulic chambers 50P and 50S of the master cylinder 5 isreplenished with the brake fluid from the reservoir tank 4, and thehydraulic pressure (the master cylinder pressure) is generated by themovement of the piston 51. The master cylinder 5 is connected to thewheel cylinders W/C via the master cylinder pipes 10M, the supply fluidpassages 11 (of the second unit 1B), and the wheel cylinder pipes 10W,and can increase the wheel cylinder hydraulic pressures. The brake fluidtransmitted out of the master cylinder 5 according to the brakeoperation performed by the driver is delivered to the master cylinderpipes 10M, and is introduced into the supply fluid passages 11 of thesecond unit 1B via the master cylinder ports 871. The master cylinder 5can increase the pressures in the wheel cylinders W/C (FL) and W/C (RR)with use of the master cylinder pressure generated in the primarychamber 50P via the fluid passage (the supply fluid passage 11P) of theP system. At the same time, the master cylinder 5 can increase thepressures in the wheel cylinders W/C (FR) and W/C (RL) with use of themaster cylinder pressure generated due to the secondary chamber 50S viathe fluid passage of the S system (the supply fluid passage 11S). Thestroke sensor 94 detects the stroke of the primary piston 51P (the pedalstroke). The first unit 1A does not include a negative pressure boosterthat boosts the brake operation force input by the driver with use of anegative pressure generated by an engine of the vehicle or a separatelyprovided negative pressure pump.

The brake fluid is delivered from the master cylinder 5 to the positivepressure chamber 601 of the stroke simulator 6 according to the brakeoperation performed by the driver, by which the pedal stroke isgenerated, and the reaction force (the pedal reaction force) of thebrake operation performed by the driver is also generated due to thebiasing force of the elastic member. When a hydraulic pressure (themaster cylinder pressure) equal to or higher than a predeterminedpressure is applied to a pressure-receiving surface of the piston 61 inthe positive pressure chamber 601, the piston 61 is axially moved towardthe backpressure chamber 602 side while pressing and compressing thespring 681 and the like. At this time, the volume of the positivepressure chamber 601 increases, and, at the same time, the volume of thebackpressure chamber 602 reduces. As a result, the brake fluidtransmitted out of the secondary chamber 50S is delivered into thepositive pressure chamber 601 via the positive pressure fluid passage74. At the same time, the brake fluid is transmitted out of thebackpressure chamber 602, and the brake fluid in the backpressurechamber 602 is discharged. The backpressure chamber 602 is connected tothe backpressure fluid passage 16 of the second unit 1B via thebackpressure pipe 10X. The brake fluid transmitted out of thebackpressure chamber 602 according to the brake operation performed bythe driver is delivered into the backpressure pipe 10X, and isintroduced into the backpressure fluid passage 16 via the backpressureport 874. The stroke simulator 6 introduces therein the brake fluid fromthe master cylinder 5 in this manner, thereby simulating hydraulicstiffness of the wheel cylinders W/C to thus imitate a feeling that thedriver would have when pressing the pedal. When the pressure in thepositive pressure chamber 601 reduces to lower than the predeterminedpressure, the piston 61 is returned to an initial position due to thebiasing force (an elastic force) of the spring 681 and the like. Whenthe piston 61 is located at the initial position, a first gap in theX-axis direction is generated between the first damper 691 and the headportion 651 of the stopper member 65, and a second gap in the X-axisdirection is generated between the second damper 692 and the bottomportion 661 of the third retainer member 66. When the first spring 681is compressed by a distance equal to or longer than the first gap in theX-axis direction according to the stroke of the piston 61 toward theX-axis negative direction side, the first damper 691 starts to beelastically deformed by being sandwiched between the protruding portion613 and the head portion 651. When the second spring 682 is compressedby a distance equal to or longer than the second gap in the X-axisdirection, the second damper 692 starts to be elastically deformed bycontacting the bottom portion 661. By these elastic deformations, animpact is reduced. Further, a characteristic about a relationshipbetween the pedal pressing force (the pedal reaction force) and thepedal stroke can be adjusted. Therefore, the pedal feeling can beimproved.

The second unit 1B supplies the brake fluid pressurized by the pump 3 tothe brake actuation units via the wheel cylinder pipes 10W, therebygenerating the brake hydraulic pressures (the wheel cylinder hydraulicpressures). The second unit 1B can supply the master cylinder pressureto each of the wheel cylinders W/C, and can also control the hydraulicpressure in each of the wheel cylinders W/C individually with use of thehydraulic pressure generated by the pump 3 independently of the brakeoperation performed by the driver with the communication blocked betweenthe master cylinder 5 and the wheel cylinders W/C. The ECU 90 receivesinputs of the values detected by the stroke sensor 94, the hydraulicsensor 91, and the like, and information regarding a running state fromthe vehicle side, and controls the opening/closing operations of theelectromagnetic valves 21 and the like and the number of rotations ofthe motor 20 (i.e., the discharge amount of the pump 3) based on aprogram installed therein, thereby controlling the wheel cylinderhydraulic pressure (the hydraulic braking force) in each of the wheelsFL to RR. By this control, the ECU 90 performs various kinds of brakecontrol (anti-lock brake control for preventing or reducing a slip ofthe wheel due to the braking, boosting control for reducing a requireddriver's brake operation force, brake control for controlling a motionof the vehicle, automatic brake control such as adaptive cruise control,regenerative cooperative brake control, and the like). The control ofthe motion of the vehicle includes vehicle behavior stabilizationcontrol such as electronic stability control. In the regenerativecooperative brake control, the ECU 90 controls the wheel cylinderhydraulic pressures so as to achieve a target deceleration (a targetbraking force) in cooperation with regenerative brake.

The ECU 90 includes a brake operation amount detection portion 90 a, atarget wheel cylinder hydraulic pressure calculation portion 90 b, apressing force brake creation portion 90 c, a boosting control portion90 d, and a control switching portion 90 e. The brake operation amountdetection portion 90 a detects a displacement amount (the pedal stroke)of the brake pedal 100 as the brake operation amount upon receiving theinput of the value detected by the stroke sensor 94. The target wheelcylinder hydraulic pressure calculation portion 90 d calculates a targetwheel cylinder hydraulic pressure. More specifically, the target wheelcylinder hydraulic pressure calculation portion 90 b calculates thetarget wheel cylinder hydraulic pressure that realizes a predeterminedboosting rate, i.e., an ideal characteristic about a relationshipbetween the pedal stroke and a brake hydraulic pressure requested by thedriver (a vehicle deceleration requested by the driver) based on thedetected pedal stroke. Further, at the time of the regenerativecooperative brake control, the target wheel cylinder hydraulic pressurecalculation portion 90 b calculates the target wheel cylinder hydraulicpressure in relation to the regenerative braking force. For example, thetarget wheel cylinder hydraulic pressure calculation portion 90 bcalculates such a target wheel cylinder hydraulic pressure that a sum ofthe regenerative braking force input from a control unit of aregenerative braking apparatus of the vehicle and a hydraulic brakingforce corresponding to the target wheel cylinder hydraulic pressure cansatisfy the vehicle deceleration requested by the driver. At the time ofthe motion control, the target wheel cylinder hydraulic pressurecalculation portion 90 b calculates the target wheel cylinder hydraulicpressure for each of the wheels FL to RR so as to, for example, realizea desired vehicle motion state based on a detected vehicle motion stateamount (a lateral acceleration or the like).

The pressing force brake creation portion 90 c deactivates the pump 3,and controls the shut-off valves 21, the SS/V IN 27, and the SS/V OUT 28in opening directions, a closing direction, and a closing direction,respectively. The fluid passage system (the supply fluid passages 11 andthe like) connecting the hydraulic chambers 50 of the master cylinder 5and the wheel cylinders W/C to each other with the shut-off valves 21controlled in the opening directions realizes the pressing force brakethat creates the wheel cylinder hydraulic pressures by the mastercylinder pressure generated with use of the pedal pressing force(non-boosting control). The SS/V OUT 28 is controlled in the closingdirection, which prohibits the stroke simulator 6 from functioning. Morespecifically, the piston 61 of the stroke simulator 6 is prohibited frombeing activated, so that the brake fluid is prohibited from beingintroduced from the hydraulic chamber 50 (the secondary chamber 50S)into the positive pressure chamber 601. This allows the wheel cylinderhydraulic pressure to be further efficiently increased. The SS/V IN 27may be controlled in an opening direction.

when the SS/V IN 27 and the SS/V OUT 28 are controlled in the closingdirection and the opening direction, respectively, with the shut-offvalves 21 controlled in the closing directions, the brake systemconnecting the first fluid pool chamber 83 and the wheel cylinders W/Cto each other (the intake oil passage 12, the discharge oil passage 13,and the like) creates the wheel cylinder hydraulic pressures by thehydraulic pressure generated with use of the pump 3, and functions as aso-called brake-by-wire system that realizes the boosting control, theregenerative cooperative control, and the like. The boosting controlportion 90 d activates the pump 3 and controls the shut-off valves 21and the communication valves 23 in the closing directions and openingdirections, respectively, thereby making the state of the second unit 1Bready to create the wheel cylinder hydraulic pressures with use of thepump 3, at the time of the brake operation performed by the driver. Bythis operation, the boosting control portion 90 d creates higher wheelcylinder hydraulic pressures than the master cylinder pressure as ahydraulic source of the discharge pressure of the pump 3 to perform theboosting control that generates a hydraulic braking force by which thedriver's braking operation force falls short. More specifically, theboosting control portion 90 d realizes the target wheel cylinderhydraulic pressure by controlling the pressure adjustment valve 24 whilekeeping the pump 3 activated at a predetermined number of rotations toadjust the brake fluid amount to be supplied from the pump 3 to thewheel cylinders W/C. In other words, the brake system 1 exerts aboosting function that assists the brake operation force by activatingthe pump 3 of the second unit 1B instead of the engine negative pressurebooster. Further, the boosting control portion 90 d controls the SS/V IN27 and the SS/V OUT 28 in the closing direction and the openingdirection, respectively. By this operation, the boosting control portion90 d causes the stroke simulator 6 to function.

Further, the ECU 90 includes a sudden brake operation statedetermination portion 90 f and a second pressing force brake creationportion 90 g. The sudden brake operation state determination portion 90f detects a brake operation state based on an input from the brakeoperation amount detection portion 90 a and the like, and determines(detects) whether the brake operation state is a predetermined suddenbrake operation state. For example, the sudden brake operation statedetermination portion 90 f determines whether an amount of a change inthe pedal stroke per unit time exceeds a predetermined threshold value.When the brake operation is determined to be the sudden brake operationstate, the control switching portion 90 e switches control so as tocreate the wheel cylinder hydraulic pressures by the second pressingforce brake creation portion 90. The second pressing force brakecreation portion 90 g activates the pump 3 and controls the shut-offvalves 21, the SS/V IN 27, and the SS/V OUT 28 in the closingdirections, the opening direction, and the closing direction. By thisoperation, the second pressing force brake creation portion 90 grealizes the second pressing force brake that creates the wheel cylinderhydraulic pressures with use of the brake fluid transmitted out of thebackpressure chamber 602 of the stroke simulator 6 until the pump 3 isready to generate sufficiently high wheel cylinder pressures. The secondpressing force brake creation portion 90 g may control the shut-offvalves 21 in the opening directions. Further, the second pressing forcebrake creation portion 90 g may control the SS/V IN 27 in the closingdirection, and, in this case, the brake fluid from the backpressurechamber 602 is supplied to the wheel cylinder W/C side via the checkvalve 270 (brought into a opened state because the pressure in the wheelcylinder W/C side is still lower than the backpressure chamber 602side). In the present embodiment, the brake fluid can be efficientlysupplied from the backpressure chamber 602 side to the wheel cylinderW/C side by controlling the SS/V IN 27 in the opening direction. Afterthat, when the brake operation state starts to be determined not to bethe sudden brake operation state and/or a predetermined conditionindicating that a discharge capacity of the pump 3 becomes sufficient issatisfied, the control switching portion 90 e switches the control so asto create the wheel cylinder hydraulic pressures by the boosting controlportion 90 d. In other words, the control switching portion 90 econtrols the SS/V IN 27 and the SSV OUT 28 in the closing direction andthe opening direction, respectively. By this operation, the controlswitching portion 90 e causes the stroke simulator 6 to function. Thecontrol switching portion 90 e may operate so as to switch the controlto the regenerative cooperative brake control after the second pressingforce brake.

The SS/V OUT 28, the SS/V IN 27, and the check valve 270 adjust a flowof the brake fluid introduced from the backpressure port 874 into thehousing 8 via the backpressure pipe 10X. These valves permit or prohibitthe inflow of the brake fluid from the master cylinder 5 into the strokesimulator 6 (the positive pressure chamber 601) by permitting orprohibiting the brake fluid introduced from the backpressure port 874into the housing 8 to be delivered or from being delivered toward one ofthe low-pressure portions (the first fluid pool chamber 83 and the wheelcylinders W/C). By this operation, these valves adjust the activation ofthe stroke simulator 6. Further, the SS/V OUT 28, the SS/V IN 27, andthe check valve 270 function as a switching portion that switches asupply destination (an outflow destination) of the brake fluidintroduced from the backpressure port 874 into the housing 8 (thebackpressure fluid passage 16) between the first fluid pool chamber 83and the wheel cylinders W/C. The control switching portion 90 e controlsthe SS/V OUT 28 in the closing direction so as to realize the secondpressing force brake until the pump 3 is ready to generate thesufficiently high wheel cylinder pressures. By this operation, the brakefluid introduced from the backpressure chamber 602 of the strokesimulator 6 into the backpressure fluid passage 16 is delivered towardthe supply fluid passages 11 via the SS/V IN 27 (the first simulatorfluid passage 17) and the check valve 270 (the bypass fluid passage170). In other words, the supply destination of the brake fluidtransmitted out of the backpressure chamber 602 is switched to the wheelcylinders W/C. Therefore, responsiveness for increasing the wheelcylinder hydraulic pressures can be ensured. When the pressure on thewheel cylinder W/C side exceeds the pressure on the backpressure chamber602 side, the check valve 270 is automatically brought into a closedstate, which prevents or reduces a reverse flow of the brake fluid fromthe wheel cylinder W/C side to the backpressure chamber 602 side. Whenthe brake operation state is determined to be the sudden brake operationstate, the control switching portion 90 e controls the SS/V OUT 28 inthe closing direction to switch the supply destination of the brakefluid to the wheel cylinders W/C. Therefore, the control switchingportion 90 e can correctly realize the second pressing force brake in asituation requiring the responsiveness for increasing the wheel cylinderhydraulic pressures. The pump 3 is a reciprocating pump, and thereforehas relatively high responsiveness. Therefore, it takes a relativelyshort time for the pump 3 to become ready to generate the sufficientwheel cylinder pressures since the pump 3 starts the activation, whichallows the second pressing force brake to be activated in a shorter timeperiod. When the predetermined condition indicating that the dischargecapacity of the pump 3 becomes sufficient is satisfied, the controlswitching portion 90 e controls the SS/V OUT 28 in the opening directionso as to cause the stroke simulator 6 to function. By this operation,the brake fluid introduced from the backpressure chamber 602 into thebackpressure fluid passage 16 is delivered toward the first fluid poolchamber 83 via the SS/V OUT 28 (the second simulator fluid passage 18).In other words, the supply destination of the brake fluid transmittedout of the backpressure chamber 602 is switched to the first fluid poolchamber 83. Therefore, an excellent pedal feeling can be ensured. Evenin the case of occurrence of such a failure that the SS/V OUT 28 isstuck in the closed state during the activation of the stroke simulator6, the piston 61 can return to the initial position due to the supply ofthe brake fluid from the first fluid pool chamber 83 side to thebackpressure chamber 602 via the check valve 280.

In the following description, the housing 8 of the second unit 1B willbe described. The housing 8 is a generally cuboidal block formed withuse of aluminum alloy as a material thereof. The outer surface of thehousing 8 includes a front surface 801, a back surface 802, a bottomsurface 803, a top surface 804, a left side surface 805, and a rightside surface 806. The front surface 801 (a first surface) is a flatsurface relatively large in area. The back surface 802 (a secondsurface) is a flat surface generally in parallel with the front surface801 and faces the front surface 801 (opposite of the housing 8 from thefront surface 801). The bottom surface 803 (a third surface) is a flatsurface connected to the front surface 801 and the back surface 802. Thetop surface 804 (a fourth surface) is a flat surface generally inparallel with the bottom surface 803 and faces the bottom surface 803(opposite of the housing 8 from the bottom surface 803). The left sidesurface 805 (a fifth surface) is a flat surface connected to the frontsurface 801, the back surface 802, the bottom surface 803, and the topsurface 804. The right side surface 806 (a sixth surface) is a flatsurface generally parallel with the left side surface 805 and faces theleft side surface 805 (opposite of the housing 8 from the left sidesurface 805). The right side surface 806 is connected to the frontsurface 801, the back surface 802, the bottom surface 803, and the topsurface 804. The front surface 801 is disposed on the Y-axis positivedirection side and extends in parallel with the X axis and the Z axiswith the housing 8 mounted on the vehicle. The back surface 802 isdisposed on the Y-axis negative direction side and extends in parallelwith the X axis and the Z axis. The top surface 804 is disposed on theZ-axis positive direction side and extends in parallel with the X axisand the Y axis. The bottom surface 803 is disposed on the Z-axisnegative direction side and extends in parallel with the X axis and theY axis. The right side surface 806 is disposed on the X-axis positivedirection side and extends in parallel with the Y axis and the Z axis.The left side surface 805 is disposed on the X-axis negative directionside and extends in parallel with the Y axis and the Z axis. In actualuse, the layout of the housing 8 in an XY plane is not limited in anymanner, and the housing 8 can be arranged in the XY plane at anyposition and in any orientation according to the vehicle layout and/orthe like.

A recessed portion 80 is formed at each of corner portions of thehousing 8 on one side where the front surface 801 is located and anotherside where the top surface 804 is located. In other words, a vertexformed by the front surface 801, the top surface 804, and the right sidesurface 806, and a vertex formed by the front surface 801, the topsurface 804, and the left side surface 805 have truncated shapes, andinclude first and second recessed portions 80A and 80B, respectively.The first recessed portion 80A is exposed (opened) on the front surface801, the top surface 804, and the left side surface 805. The secondrecessed portion 80B is exposed (opened) on the front surface 801, thetop surface 804, and the right side surface 806. The first recessedportion 80A includes a first flat surface portion 807, a second flatsurface portion 808, and a third flat surface portion 809. The firstflat surface portion 807 extends orthogonally to the Y axis and inparallel with an XZ plane. The second flat surface portion 808 extendsorthogonally to the X axis and generally in parallel with a YZ plane.The third flat surface 809 extends in the Y-axis direction and forms anangle of approximately 50 degrees with respect to the right side surface806 in a counterclockwise direction as viewed from the Y-axis positivedirection side. The second flat surface portion 808 and the third flatsurface portion 809 are connected to each other smoothly via a concavedcurved surface extending in the Y-axis direction. The second recessedportion 80B includes a first flat surface portion 807, a second flatsurface portion 808, and a third flat surface portion 809. The thirdflat surface portion 809 extends in the Y-axis direction and forms anangle of approximately 50 degrees with respect to the left side surface806 in a clockwise direction as viewed from the Y-axis positivedirection side. A configuration of the second recessed portion 80B otherthan that is similar to the first recessed portion 80A. The first andsecond recessed portions 80A and 80B are generally symmetric withrespect to the YZ plane at a center of the housing 8 in the X-axisdirection.

The housing 8 includes a cam containing hole 81, a plurality of (five)cylinder containing holes 82A to 82E, the first fluid pool chamber 83, asecond fluid pool chamber 84, a plurality of fixation holes 85, aplurality of valve containing holes, a plurality of sensor containingholes, a power source hole 86, the plurality of ports 87, the pluralityof fluid passages 11, and the like. These holes and ports are formedwith use of a drill or the like. The cam containing hole 81 has abottomed cylindrical shape extending in the Y-axis direction, and isopened on the front surface 801. A central axis O of the cam containinghole 81 is disposed at a position of the front surface 801 that isgenerally central in the X-axis direction and slightly offset from acenter in the Z-axis direction toward the Z-axis negative directionside. The bottom surface 803 is positioned on the Z-axis negativedirection side with respect to the central axis O, and the firstrecessed portion 80A and the second recessed portion 80B are positionedon the Z-axis positive direction side with respect to the central axisO.

Each of the cylinder containing holes 82 has a stepped cylindrical shapeand has a central axis extending in a radial direction of the camcontaining hole 81 (a radial direction around the central axis O). Thehole 82 includes a small-diameter portion 820 on one side closer to thecam containing hole 81, a large-diameter portion 821 on the other sidefarer away from the cam containing hole 81, and an intermediate-diameterportion 822 between the small-diameter portion 820 and thelarge-diameter portion 821. A part 823 of the intermediate-diameterportion 822 on the one side closer to the cam containing hole 81functions as an intake port, and the large-diameter portion 821functions as a discharge port. The plurality of holes 82A to 82E isdisposed generally evenly (at generally even intervals) in a directionextending around the central axis O. An angle formed by the central axesof the holes 82 adjacent to each other in the direction extending aroundthe central axis O is approximately 72 degrees (falls within apredetermined range including 72 degrees). The plurality of holes 82A to82E is arrayed in one row along the Y-axis direction, and is disposed ona Y-axis positive direction side of the housing 8. In other words, thecentral axes of these holes 82A to 82E are located in a same plane αgenerally orthogonal to the central axis O. The plane α extendsgenerally in parallel with the front surface 801 and the back surface802 of the housing 8, and is located closer to the front surface 801than to the back surface 802. The intake port 823 of each of the holes82A to 82E is connected to one another via a first communication fluidpassage. The discharge port 821 of each of the holes 82A to 82E isconnected to one another via a second communication fluid passage.

Each of the holes 82A to 82E is disposed inside the housing 8 in thefollowing manner. The hole 82A extends from the bottom surface 803 tothe Z-axis positive direction side. The hole 82B extends from a portionof the left side surface 805 that is positioned on a lower side in theZ-axis negative direction with respect to the central axis O to theX-axis positive direction side and the Z-axis positive direction side.The hole 82C extends from the first recessed portion 80A to the X-axispositive direction side and the Z-axis negative direction side. The hole82D extends from the second recessed portion 80B to the X-axis negativedirection side and the Z-axis negative direction side. The hole 82Eextends from a portion of the right side surface 806 that is positionedon the lower side in the Z-axis negative direction with respect to thecentral axis O to the X-axis negative direction side and the Z-axispositive direction side. On the Z-axis negative direction side withrespect to the central axis O, the hole 82A is positioned at the sameposition in the X-axis direction as the central axis O, and the holes82B and 82E are disposed on opposite sides of the central axis O (thehole 82A) from each other in the X-axis direction. On the Z-axispositive direction side with respect to the central axis O, the holes82C and 82D are disposed on opposite sides of the central axis O fromeach other in the X-axis direction. The small-diameter portion 820 ofeach of the holes 82A to 82E is opened on an inner peripheral surface ofthe cam containing hole 81. An end of the hole 82A on the large-diameterportion 821 side is opened at a portion of the bottom surface 803 thatis generally central in the X-axis direction and located on the Y-axispositive direction side. An end of the hole 82B on the large-diameterportion 821 side is opened on a portion of the left side surface 805that is located on the Y-axis positive direction side and the Z-axisnegative direction side. An end of the hole 82E on the large-diameterportion 821 side is opened on a portion of the right side surface 806that is located on the Y-axis positive direction side and the Z-axisnegative direction side. Ends of the holes 82C and 82D on large-diameterportion 821 sides are opened on the first and second recessed portions80A and 80B, respectively. More specifically, more than half of the endon the large-diameter portion 821 side is opened on the third flatsurface portion 809, and a remaining portion thereof is opened on thesecond flat surface portion 808. The third flat surface portion 809extends generally orthogonally to the central axes of the holes 82C and82D.

The first fluid pool chamber 83 has a bottomed cylindrical shape havinga central axis extending in the Z-axis direction. The first fluid poolchamber 83 is opened on a portion of the top surface 804 that isgenerally central in the X-axis direction and offset toward the Y-axispositive direction, and is disposed from the top surface 804 into thehousing 8. The first fluid pool chamber 83 (a bottom portion thereof onthe Z-axis negative direction side) is disposed on a Z-axis positivedirection side of each of the cylinder containing holes 82 with respectto the intake port 823. The first fluid pool chamber 83 is formed in aregion between the cylinder containing holes 82C and 82D adjacent toeach other in the direction extending around the central axis O on theZ-axis positive direction side with respect to the central axis O. Thefirst fluid pool chamber 83 and the holes 82C and 82D partially overlapeach other in the Y-axis direction (as viewed from the X-axisdirection). The first fluid pool chamber 83 and the intake port 823 ofeach of the holes 82A to 82E are connected to each other via the intakefluid passage 12. The second fluid pool chamber 84 has a bottomedcylindrical shape having a central axis extending in the Z-axisdirection. The second fluid pool chamber 84 is opened on a portion ofthe bottom surface 803 that is located on the X-axis negative directionside and offset toward the Y-axis positive direction, and is disposedfrom the bottom surface 803 into the housing 8. The second fluid poolchamber 84 is formed in a region between the cylinder containing holes82A and 82B adjacent to each other in the direction extending around thecentral axis O on the Z-axis negative direction side with respect to thecentral axis O. The cylinder containing hole 82A and the second fluidpool chamber 84 partially overlap each other in the Y-axis direction (asviewed from the X-axis direction). The cam containing hole 81 and thesecond fluid pool chamber 84 are connected to each other via the drainfluid passage 19. One end of the drain fluid passage 19 is opened on aportion on an inner peripheral surface of the cam containing hole 81that is located on the Y-axis negative direction side and the Z-axisnegative direction side, and an opposite end of the drain fluid passage19 is opened on an outer peripheral edge of the bottom surface of thesecond fluid pool chamber 84 on the Z-axis positive direction side.

The plurality of valve containing holes each has a bottomed cylindricalshape, and extends in the Y-axis direction to be opened on the backsurface 802. The plurality of valve containing holes is arrayed in onerow along the Y-axis direction, and is disposed on a Y-axis negativedirection side of the housing 8. The cylinder containing holes 82 andthe valve containing holes are arranged along the Y-axis direction. Theplurality of valve containing holes at least partially overlaps thecylinder containing holes 82 as viewed from the Y-axis direction. Mostof the plurality of valve containing holes is contained in a circleconnecting ends of the plurality of cylinder containing holes 82 on thelarge-diameter portion 821 sides (the other sides farer away from thecentral axis O). Alternatively, an outer periphery of this circle andthe valve containing holes at least partially overlap each other. Avalve portion of the electromagnetic valve is fitted and a valve portionthereof is contained in each of the valve containing holes. The bypassfluid passage 120 and the check valve 220 are each formed by a cup-likeseal member or the like set in the valve containing hole. The pluralityof sensor containing holes each has a bottomed cylindrical shape havinga central axis extending in the Y-axis direction, and is opened on theback surface 802. A pressure-sensitive portion such as the hydraulicsensor 91 is contained in each of the sensor containing portions. Thepower source hole 86 has a cylindrical shape and penetrates through thehousing 8 (between the front surface 801 and the back surface 802) inthe Y-axis direction. The hole 86 is disposed at a portion of thehousing 8 that is located at a generally central position in the X-axisdirection and on the Z-axis positive direction side. The hole 86 isdisposed (formed) in a region between the cylinder containing holes 82Cand 82D adjacent to each other.

The intake port 873 is an opening portion of the first fluid poolchamber 83 on the top surface 804, and is opened on an upper side in thevertical direction. The port 873 is opened at a portion of the topsurface 804 that is located on the central side in the X-axis directionand offset toward the Y-axis positive direction (a position closer tothe front surface 801 than the wheel cylinder ports 872 are). The port873 is disposed on the Z-axis positive direction side with respect tothe intake port 823 of each of the cylinder containing holes 82A to 82E.The cylinder containing holes 82C and 82D sandwich the port 873 asviewed from the Y-axis direction. The opening of each of the cylindercontaining holes 82C and 82D and the port 873 partially overlap eachother in the Y-axis direction (as viewed from the X-axis direction). Themaster cylinder ports 871 each have a bottomed cylindrical shape havinga central axis extending in the Y-axis direction, and are opened onportions that are an end of the front surface 801 on the Z-axis positivedirection side and is sandwiched between the recessed portions 80A and80B. The primary port 871P is disposed on the X-axis positive directionside, and the secondary port 871S is disposed on the X-axis negativedirection side. Both the ports 871P and 871S are arranged in the X-axisdirection, and sandwich the first fluid pool chamber 83 in the X-axisdirection (as viewed from the Y-axis direction). The ports 871P and 871Sare sandwiched between the first fluid pool chamber 83 and the cylindercontaining holes 82C and 82D in the direction extending around thecentral axis O (as viewed from the Y-axis direction), respectively. Thewheel cylinder ports 872 each have a bottomed cylindrical shape having acentral axis extending in the Z-axis direction, and is opened on aY-axis negative direction side of the top surface 804 (a position closerto the back surface 802 than to the front surface 801). The ports 872 ato 872 d are arranged in one row in the X-axis direction. The two ports872 a and 872 d of the P system are disposed on the X-axis positivedirection side, and the two ports 872 b and 872 c of the S system aredisposed on the X-axis negative direction side. The port 872 a isdisposed on the X-axis positive direction side with respect to the port872 d in the P system, and the port 872 b is disposed on the X-axisnegative direction side with respect to the port 872 c in the S system.The ports 872 c and 872 d sandwich the intake port 873 (the first fluidpool chamber 83) as viewed from the Y-axis direction. The ports 872 andthe first fluid pool chamber 83 partially overlap each other in theZ-axis direction. Openings of the ports 872 and the intake port 873 (anopening of the first fluid pool chamber 83) partially overlap each otherin the X-axis direction (as viewed from the Y-axis direction). Theintake port 873 (the first fluid pool chamber 83) is located inside aquadrilateral defined by connecting the ports 871P, 871S, 872 c, and 872d (centers thereof) with line segments, as viewed from the Z-axisdirection. The first fluid pool chamber 83 is disposed in a regionsurrounded by the master cylinder ports 871 and the wheel cylinder ports872. The backpressure port 874 has a bottomed cylindrical shape having acentral axis extending in the X-axis direction, and is opened on aportion of the right side surface 806 that is located on the Y-axisnegative direction side and offset from the central axis O toward theZ-axis negative direction side. The plurality of fluid passages 11 andthe like connect the ports 87, the fluid pool chambers 83 and 84, thecylinder containing holes 82, the valve containing holes, and thehydraulic sensor containing holes to one another.

The plurality of fixation holes 85 include bolt holes 851 to 853 forfixing the motor (refer to FIG. 7), bolt holes 854 to 857 for fixing theECU (refer to FIGS. 5 to 7), and a bolt hole 858 and a pin hole 859 forfixing the housing (refer to FIGS. 4 and 5). The bolt holes 851 to 853each have a bottomed cylindrical shape having a central axis extendingin the Y-axis direction, and are opened on the front surface 801. Theholes 851 to 853 are located on the Y-axis positive direction side ofthe housing 8, and partially overlap the cylinder containing hole 82 inthe Y-axis direction. The holes 851 to 853 are provided at positionsgenerally symmetric with respect to the central axis O of the camcontaining hole 81. Distances from the central axis O to the individualholes 851 to 853 are generally equal to one another. The holes 852 and853 are located on opposite sides of the central axis O from each otherin the X-axis direction and on the Z-axis positive direction side withrespect to the central axis O. The holes 852 and 853 are locatedadjacent to the cylinder containing holes 82C and 82D (thelarge-diameter portions 821 thereof) on one sides closer to the sidesurfaces 805 and 805 with respect to the cylinder containing holes 82Cand 82D (on opposite sides of the cylinder containing holes 82 from thefirst fluid pool chamber 83), respectively, and are also locatedadjacent to the third flat surface portions 809 of the recessed portions80A and 80B, respectively. The hole 851 is located on the X-axispositive direction side with respect to the cylinder containing hole 82Aand on the Z-axis negative direction side with respect to the centralaxis O. The hole 851 is located adjacent to the cylinder containing hole82A (the large-diameter portion 821 thereof), and is also locatedadjacent to the bottom surface 803 on an opposite side of the cylindercontaining hole 82A from the second fluid pool chamber 84. The boltholes 854 to 857 each have a cylindrical shape having a central axisextending in the Y-axis direction, and penetrate through the housing 8.The holes 854 and 855 are located on one side closer to the bottomsurface 803, and the holes 856 and 857 are located on the other sidecloser to the top surface 804. The holes 854 and 855 are positioned atcorner portions sandwiched between the bottom surface 803 and the sidesurfaces 805 and 806, and are opened on the front surface 801 and thebacks surface 802. The holes 856 and 857 are positioned at cornerportions sandwiched between the top surface 804 and the second flatsurface portions 808 of the recessed portions 80 as viewed from theY-axis direction, and are opened on the first flat surfaces 807 of therecessed portions 80 and the back surface 802. The hole 856 is locatedadjacent to the wheel cylinder port 872 b and is sandwiched between theports 872 b and 872 c in the X-axis direction. The hole 857 is locatedadjacent to the wheel cylinder port 872 a and is sandwiched between theports 872 a and 872 d in the X-axis direction. The bolt holes 858A and858B are positioned on the Z-axis negative direction side with respectto the central axis O. The holes 858A and 858B each have a bottomedcylindrical shape having a central axis extending in the Y-axisdirection, and are opened on both ends of the front surface 801 in theX-axis direction. The holes 858A and 858B are located on the Y-axispositive direction side of the housing 8, and partially overlap thecylinder containing holes 82 in the Y-axis direction. The holes 858A and858B are located adjacent to the side surfaces 805 and 806, and aresandwiched between the cylinder containing holes 82B and 82E and thebolt holes 855 and 854 in the Z-axis direction, respectively. The hole858A on the X-axis negative direction side is sandwiched between theleft side surface 805 and the second fluid pool chamber 84. The hole858A is positioned on an opposite side of a vicinity of the central axisO from the primary port 871P. The hole 858B on the X-axis positivedirection side is positioned on an opposite side of the vicinity of thecentral axis O from the secondary port 871S. The hole 858C is positionedon the Z-axis positive direction side with respect to the central axisO. The hole 858C has a bottomed cylindrical shape having a central axisextending in the X-axis direction, and is opened at a generally centralportion of the right side surface 806 in the Y-axis direction. The hole858C is opened while being located adjacent to a corner portionsandwiched between the first flat surface portion 807 and the third flatsurface portion 809 of the second recessed portion 80B as viewed fromthe X-axis direction. The hole 858C is positioned on an opposite side ofthe vicinity of the central axis O from the hole 858A. The pin hole 859has a bottomed cylindrical shape having a central axis extending in theZ-axis direction, and is opened on a portion of the bottom surface 803that is located at a generally central position in the X-axis directionand on the Y-axis negative direction side. The pin hole 859 is locatedadjacent to a Y-axis negative direction side of the cylinder containinghole 82A. The pin hole 859 overlaps the cylinder containing hole 82A asviewed from the Y-axis direction.

(Fixation of Motor)

The motor 20 is disposed and a motor housing 200 is attached on thefront surface 801 of the housing 8. The front surface 801 functions as amotor attachment surface. The bolt holes 851 to 853 function as afixation portion for fixing the motor 20 to the housing 8. The motor 20includes the motor housing 200. The motor housing 200 has a bottomedcylindrical shape, and includes a cylindrical portion 201, a bottomportion 202, and a flange portion 203. The cylindrical portion 201contains a magnet as a stator, a rotor, and the like on an innerperipheral side, if being assumed to be a brushed DC motor by way ofexample. A rotational shaft of the motor 20 extends on a central axis ofthe cylindrical portion 201. The bottom portion 202 closes one axialside of the cylindrical portion 201. The flange portion 203 is providedat an end of the cylindrical portion 201 on an opposite axial side (anopening side), and flares radially outwardly from an outer peripheralsurface of the cylindrical portion 201. The flange portion 203 includesfirst, second, and third protruding portions 203 a, 203 b, and 203 c. Abolt hole penetrates through each of the protruding portions 203 a to203 c. A bolt b1 is inserted in each of the bolt holes, and the bolt b1is fastened in each of the bolt holes 851 to 853 of the housing 8. Theflange portion 203 is fastened onto the front surface 801 by the boltsb1. A conductive member (a power source connector) for power supply isconnected to the rotor via a brush. The conductive member (the powersource connector) is contained (attached) in the power source hole 86,and protrudes from the back surface 802 toward the Y-axis negativedirection side. The master cylinder ports 871 are positioned on theZ-axis positive direction side with respect to the central axis O and onthe Z-axis positive direction side with respect to the motor 20 (themotor housing 200).

(Pump)

FIG. 7 illustrates a cross section of the second unit 1B taken along theplane α. The central axis (an axial line) of the rotational shaft of themotor 20 generally coincides with the central axis O of the camcontaining hole 81. A rotational driving shaft 300, which is arotational shaft and a driving shaft of the pump 3, and a cam unit 30are contained in the cam containing hole 81 (inside the housing 8). Therotational driving shaft 300 is the driving shaft of the pump 3. Therotational driving shaft 300 is fixedly coupled with the rotationalshaft of the motor 20 in such a manner that a central axis thereofextends on an extension of the central axis of the rotational shaft ofthe motor 20, and is rotationally driven by the motor 20. The centralaxis of the rotational driving shaft 300 generally coincides with thecentral axis O. The rotational driving shaft 300 rotates around thecentral axis O integrally with the rotational shaft of the motor 20. Thecam unit 30 is provided on the rotational driving shaft 300. The camunit 30 includes a cam 301, a driving member 302, and a plurality ofrolling members 303. The cam 301 is a columnar eccentric cam, and has acentral axis P eccentric with respect to the central axis O of therotational driving shaft 300. The central axis P extends generally inparallel with the central axis O. The cam 301 swings while rotatingaround the central axis O integrally with the rotational driving shaft300. The driving member 302 has a cylindrical shape, and is disposed onan outer peripheral side of the cam 301. A central axis of the drivingmember 302 generally coincides with the central axis P. The drivingmember 302 is rotatable around the central axis P relative to the cam301. The driving member 302 has a similar configuration to an outer raceof a rolling bearing. The plurality of rolling members 303 is disposedbetween an outer peripheral surface of the cam 301 and an innerperipheral surface of the driving member 302. The rolling members 303are needle rollers, and extend along a direction of the central axis ofthe rotational driving shaft 300.

The pump 3 is a radial plunger pump in the form of a fixed cylinder, andincludes the housing 8, the rotational driving shaft 300, the cam unit30, and the plurality of (five) pump portions 3A to 3E. The pumpportions 3A to 3E are each a plunger pump (a piston pump) as areciprocating pump, and are activated by the rotation of the rotationaldriving shaft 300. The brake fluid as the hydraulic fluid is introducedand discharged according to a reciprocating movement of plungers(pistons) 36. The cam unit 30 has a function of converting therotational movement of the rotational driving shaft 300 into thereciprocating movement of the plungers 36. When a configuration of eachof the pump portions 3A to 3E is distinguished from each other, indicesA to E are added to the reference numerals thereof. The individualplungers 36 are disposed around the cam unit 30, and are each containedin the cylinder containing hole 82. A central axis 360 of the plunger 36generally coincides with the central axis of the cylinder containinghole 82, and extends in a radial direction of the rotational drivingshaft 300. In other words, the plungers 36 as many as the number of thecylinder containing holes 82 (five) are provided, and extend radiallywith respect to the central axis O. The plungers 36A to 36E are disposedgenerally evenly in a direction extending around the rotational drivingshaft 300 (hereinafter simply referred to as a circumferentialdirection), i.e., at generally even intervals in a direction in whichthe rotational driving shaft 300 rotates. Central axes 360A to 360E ofthese plungers 36A to 36E are located on the same plane α. Theseplungers 36A to 36E are driven by the same rotational driving shaft 300and the same cam unit 30.

The pump portion 3A includes a cylinder sleeve 31, a filter member 32, aplug member 33, a guide ring 34, a first seal ring 351, a second sealring 352, the plunger 36, a return spring 37, an intake valve 38, and adischarge valve 39, and these components are set in the cylindercontaining hole 82. The cylinder sleeve 31 has a bottomed cylindricalshape, and a hole 311 penetrates through a bottom portion 310 thereof.The cylinder sleeve 31 is fixed in the cylinder containing hole 82. Acentral axis of the cylinder sleeve 31 generally coincides with thecentral axis 360 of the cylinder containing hole 82. An end 312 of thecylinder sleeve 31 on an opening side is disposed on theintermediate-diameter portion 822 (the intake port 823), and the bottomportion 310 is disposed on the large-diameter portion (discharge port)821. The filter member 32 has a bottomed cylindrical shape, and a hole321 penetrates through a bottom portion 320 thereof and a plurality ofopening portions also penetrates through a side wall portion thereof. Afilter is set on each of these opening portions. An end 323 of thefilter member 32 on an opening side is fixed to the end 312 of thecylinder sleeve 31 on the opening side. The bottom portion 320 isdisposed on the small-diameter portion 820. A central axis of the filtermember 32 generally coincides with the central axis 360 of the cylindercontaining hole 82. A gap is generated between an outer peripheralsurface where the opening portion of the filter member 32 is opened andan inner peripheral surface of the cylinder containing hole 82 (theintake port 823). The first communication fluid passage is incommunication with the intake port 823 and the above-described gap. Theplug member 33 has a columnar shape, and includes a recessed portion 330and a groove on one axial side thereof. This groove extends radially toconnect the recessed portion 330 and an outer peripheral surface of theplug member 33 to each other, and is in communication with the dischargeport 821. The above-described one axial side of the plug member 33 isfixed to the bottom portion 310 of the cylinder sleeve 31. A centralaxis of the plug member 33 generally coincides with the central axis 360of the cylinder containing hole 82. The plug member 33 is fixed to thelarge-diameter portion 821, and closes an opening of the cylindercontaining hole 82 on the outer peripheral surface of the housing 8. Thesecond communication fluid passage is in communication with thedischarge port 821 and the above-described groove of the plug member 33.The guide ring 34 has a cylindrical shape, and is fixed on the one sideof the cylinder containing hole 82 that is located closer to the camcontaining hole 81 (the small-diameter portion 82) with respect to thefilter member 32. A central axis of the guide ring 34 generallycoincides with the central axis 360 of the cylinder containing hole 82.The first seal ring 351 is set between the guide ring 34 and the filtermember 32 in the cylinder containing hole 82 (the small-diameter portion820).

The plunger 36 has a columnar shape, and includes an end surface(hereinafter referred to as a plunger end surface) 361 on one axial sidethereof and a flange portion 362 on an outer periphery on an oppositeaxial side thereof. The plunger end surface 361 has a flat surface-likeshape extending in a direction generally orthogonal to the central axis360 of the plunger 36, and has a generally circular shape centered atthe central axis 360. The plunger 36 includes an axial hole 363 and aradial hole 364 therein. The axial hole 363 extends on the central axis360 to be opened on an end surface of the plunger 36 on theabove-described opposite axial side. The radial hole 364 extends in aradial direction of the plunger 36 to be opened on an outer peripheralsurface on the above-described one axial side with respect to the flangeportion 362 and to be also connected to the above-described one axialside of the axial hole 363. A check valve case 365 is fixed at an end ofthe plunger 36 on the above-described opposite axial side. The checkvalve case 365 has a bottomed cylindrical shape made from a thin plate,and includes a flange portion 366 on an outer periphery of an endthereof on an opening side and a plurality of holes 368 penetratingthrough a side wall portion and a bottom portion 367 thereof. The end ofthe check valve case 365 on the opening side is fitted to the end of theplunger 36 on the above-described opposite axial side. The second sealring 352 is set between the flange portion 366 of the check valve case365 and the flange portion 362 of the plunger 36. The above-describedopposite axial side of the plunger 36 is inserted in an inner peripheralside of the cylinder sleeve 31, and the plunger portion 362 is guidedand supported by the cylinder sleeve 31. The above-described one axialside of the plunger 36 with respect to the radial hole 364 is insertedin an inner peripheral side (the hole 321) of the bottom portion 320 ofthe filter member 32, an inner peripheral side of the first seal ring351, and an inner peripheral side of the guide ring 34, and is guidedand supported by them. The central axis 360 of the plunger 36 generallycoincides with the central axis of the cylinder sleeve 31 and the like(the cylinder containing hole 82). The end of the plunger 36 on theabove-describe one axial side (the plunger end surface 361) protrudes toinside the cam containing hole 81.

The return spring 37 is a compression coil spring, and is set on theinner peripheral side of the cylinder sleeve 31. One end and an oppositeend of the return spring 37 are set on the bottom portion 310 of thecylinder sleeve 31 and the flange portion 366 of the check valve case365, respectively. The return spring 37 constantly biases the plunger 36toward the one side where the cam containing hole 81 is located relativeto the cylinder sleeve 31 (the cylinder containing hole 82). The intakevalve 38 includes a ball 380 as a valve body and a return spring 381,and these are contained on an inner peripheral side of the check valvecase 365. A valve seat 369 is provided around the opening of the axialhole 363 on the end surface of the plunger 36 on the above-describedopposite axial side. The ball 380 is seated on the valve seat 369, bywhich the axial hole 363 is closed. The return spring 381 is acompression coil spring, and one end and an opposite end thereof are seton the bottom portion 367 of the check valve case 365 and the ball 380,respectively. The return spring 381 constantly biases the ball 380toward one side where the valve seat 369 is located relative to thecheck valve case 365 (the plunger 36). The discharge valve 39 includes aball 390 as a valve body and a return spring 391, and these arecontained in the recessed portion 330 of the plug member 33. A valveseat 313 is provided around an opening portion of the through-hole 311at the bottom portion 310 of the cylinder sleeve 31. The ball 390 isseated on the valve seat 313, by which the through-hole 311 is closed.The return spring 391 is a compression coil spring, and one end and anopposite end thereof are set on a bottom surface of the recessed portion330 and the ball 390, respectively. The return spring 391 constantlybiases the ball 390 toward one side where the valve seat 313 is located.

Inside the cylinder containing hole 82, a space R1 on one side closer tothe cam containing hole 82 with respect to the flange portion 362 of theplunger 36 is a space on the intake side in communication with the firstcommunication fluid passage. More specifically, a space extending fromthe above-described gap between the outer peripheral surface of thefilter member 32 and the inner peripheral surface (the intake port 823)of the cylinder containing hole 82, passing through the plurality ofopenings of the filter member 32, and a gap between an outer peripheralsurface of the plunger 36 and an inner peripheral surface of the filtermember 32, and leading to the radial hole 364 and the axial hole 363 ofthe plunger 36 functions as the intake-side space R1. This intake-sidespace R1 is prevented from communicating with the cam containing hole 81by the first seal ring 351. Inside the cylinder containing hole 82, aspace R3 between the cylinder sleeve 31 and the plug member 33 is adischarge-side space in communication with the second communicationfluid passage. More specifically, a space extending from theabove-described groove of the plug member 33 to the discharge port 821functions as the discharge-side space R3. On the inner peripheral sideof the cylinder sleeve 31, a volume of a space R2 between the flangeportion 362 of the plunger 36 and the bottom portion 310 of the cylindersleeve 31 changes due to reciprocation (a stroke) of the plunger 36relative to the cylinder sleeve 31. This space R2 is in communicationwith the intake-side space R1 due to opening of the intake valve 38, andis in communication with the discharge-side space R3 due to opening ofthe discharge valve 39. The plunger 36 of the pump portion 3A exerts apump function by reciprocating. More specifically, when the plunger 36is stroked toward the cam containing hole 81 (the central axis O), thevolume of the space R2 increases and a pressure in R2 reduces. Due toclosing of the discharge valve 39 and the opening of the intake valve38, the brake fluid as the hydraulic fluid is introduced from theintake-side space R1 to the space R2, and the brake fluid is suppliedfrom the first communication fluid passage into the space R2 via theintake port 823. When the plunger 36 is stroked away from the camcontaining hole 81, the volume of the space R2 reduces and the pressurein R2 increases. Due to closing of the intake valve 38 and the openingof the discharge valve 39, the brake fluid is transmitted out of thespace R2 into the discharge-side space R3, and the brake fluid issupplied into the second communication fluid passage via the dischargeport 821. The other pump portions 3B to 3E also have similarconfigurations. The brake fluid discharged to the second communicationfluid passage by each of the pump portions 3A to 3E is collected intothe single discharge fluid passage 13, and is used in common by the twohydraulic circuit systems.

(Fixation of ECU)

The ECU 90 is disposed and attached on the back surface 802 of thehousing 8. In other words, the ECU 90 is provided integrally with thehousing 8. The ECU 90 includes a control board and a control unithousing (case) 901. The control board controls states of power supply tothe motor 20 and the solenoids of the electromagnetic valves 21 and thelike. Various kinds of sensors that detect the motion state of thevehicle, such as an acceleration sensor that detects an acceleration ofthe vehicle, and an angular speed sensor that detects an angular speed(a yaw rate) of the vehicle, may be mounted on the control board.Further, a combination sensor (a combined sensor) formed by unitizingthese sensors may be mounted on the control board. The control board iscontained in the case 901. The case 901 is a cover member attached tothe back surface 802 (the bolt holes 854 to 857) of the housing 8 withuse of bolts b2. The back surface 802 functions as a case attachmentsurface (a cover member attachment surface). The bolt holes 854 to 857function as a fixation portion for fixing the ECU 90 to the housing 8.Head portions of the bolts b2 are disposed on one side where the frontsurface 801 of the housing 8 is located. Shaft portions of the bolts b2penetrate through the bolt holes 854 to 857, and distal end sides of theshaft portions are threadably engaged with female screws on the otherside where the case 901 is located. The case 901 is fastened and fixedto the back surface 802 of the housing 8 with the aid of axial forces ofthe bolts b2. The head portions b21 of the bolts b2 protrude in thefirst recessed portion 80A and the second recessed portion 80B,respectively. The head portions b21 are contained inside the recessedportions 80 and do not protrude beyond the front surface 801 toward theY-axis positive direction side.

The case 901 is a cover member made from a resin material, and includesa board containing portion 902 and a connector portion 903. The boardcontaining portion 902 contains therein the control board and parts ofthe solenoids of the electromagnetic valves 21 and the like (hereinafterreferred to as the control board and the like). The board containingportion 902 includes a cover portion 902 a. The cover portion 902 acovers the control board and the like and isolates them from outside.The control board is mounted on the board containing portion 902generally in parallel with the back surface 802. Terminals of thesolenoids of the electromagnetic valves 21 and the like, terminals ofthe hydraulic sensor 91 and the like, and the conductive member from themotor 20 protrude from the back surface 802. The above-describedterminals and conductive member extend toward the Y-axis negativedirection side to be connected to the control board. The connectorportion 903 is disposed on an X-axis negative direction side of theboard containing portion 902 with respect to the above-describedterminals and conductive member, and protrudes toward a Y-axis positivedirection side of the board containing portion 902. The connectorportion 903 is disposed on a slightly outer side (the X-axis negativedirection side) with respect to the left side surface 805 of the housing8 as viewed from the Y-axis direction. A terminal of the connectorportion 903 is exposed toward the Y-axis positive direction side, andalso extends toward the Y-axis negative direction side to be connectedto the control board. Each terminal of the connector portion 903 (whichis exposed toward the Y-axis positive direction side) is connectable toan external apparatus or the stroke sensor (hereinafter referred to asthe external apparatus and the like). An electric connection isestablished between the external apparatus and the like and the controlboard (the ECU 90) by insertion of another connector connected to theexternal apparatus and the like into the connector portion 903 from theY-axis positive direction side. Further, power is supplied from anexternal power source (a battery) to the control board via the connectorportion 903. The conductive member functions as a connection portionthat electrically connects the control board and the motor 20 (the rotorthereof) to each other, and power is supplied from the control board tothe motor 20 (the rotor thereof) via the conductive member.

(Fixation of Housing)

FIG. 8 is a perspective view illustrating the second unit 1B with thepin PIN, bolts B2, insulators 105 and 108, and the like attached theretoas viewed from the X-axis positive direction side, the Y-axis positivedirection side, and the Z-axis positive direction side. FIG. 9 is aperspective view illustrating the second unit 1B in a state mounted on amount 100 as viewed from the X-axis positive direction side, the Y-axispositive direction side, and the Z-axis positive direction side. FIG. 10is a front view illustrating the second unit 1B in the state mounted onthe mount 100 as viewed from the Y-axis positive direction side. Thehousing 8 and like are illustrated in cross-section taken along theplane α, and a second mount portion 102, the bolts B2, and the like areindicated by broken lines.

The mount 100 is a base formed by bending and folding a metallic plate,and is fastened and fixed to the vehicle boy side (normally, a mountingmember provided on a bottom surface or a side wall in the engine roomand formed so as to be fitted to the mount 100) with use of bolts. Themount 100 may be fixed to the vehicle body side by welding. The mount100 integrally includes a first mount portion 101, the second mountportion 102, and leg portions 104. The first mount portion 101 isdisposed generally in parallel with the X axis and the Y axis. Aninsulator hole is formed on a portion of the first mount portion 101that is generally central in the X-axis direction and located on theY-axis negative direction side. The second mount portion 102 extendsfrom an end of the first mount portion 101 in the Y-axis positivedirection toward the Z-axis positive direction side. An end edge of thesecond mount portion 102 in the Z-axis positive direction is curved in aconcaved manner so as to conform to a shape of the cylindrical portion201 of the motor housing 200. Ends of the second mount portion 102 onthe both sides in the X-axis direction include recessed portions 102 aon ends in the Z-axis positive direction, respectively. The recessedportion 102 a on the X-axis positive direction side is opened on theZ-axis positive direction side and the X-axis positive direction side.The recessed portion 102 b on the X-axis negative direction side isopened on the Z-axis positive direction side and the X-axis negativedirection side. The leg portions 104 include leg portions 104 a to 104f. The leg portion 102 a extends from an end of the first mount portion101 in the X-axis negative direction to the Z-axis negative directionside. The leg portion 102 b extends from an end of the first mountportion 101 in the X-axis positive direction to the Z-axis negativedirection side. The leg portion 104 c extends from an end of the firstmount portion 101 in the Y-axis negative direction to the Z-axisnegative direction side. The leg portion 102 d extends from an end ofthe leg portion 102 a in the Z-axis negative direction to the X-axisnegative direction side. A plurality of bolt holes is formed on the legportion 102 d so as to be arranged in the Y-axis direction. The boltsfor fixing the mount 100 to the vehicle body side are inserted intothese holes from the Z-axis positive direction side. The leg portion 102e extends from an end of the leg portion 102 b in the Z-axis negativedirection to the X-axis positive direction side. A plurality of boltholes is formed on the leg portion 102 e so as to be arranged in theY-axis direction. The bolts for fixing the mount 100 to the vehicle bodyside are inserted into these holes from the Z-axis positive directionside. The leg portion 102 f extends from an end of the leg portion 102 cin the Z-axis negative direction to the Y-axis negative direction side.A plurality of bolt holes is formed on the leg portion 102 f so as to bearranged in the X-axis direction. The bolts for fixing the mount 100 tothe vehicle body side are inserted into these holes from the Z-axispositive direction side.

The pin PIN is press-fitted and fixed in the pin hole 859 of the housing8. The pin PIN is inserted in the insulator hole of the first mountportion 101. The pin PIN fixes the bottom surface 803 of the housing 8to the first mount portion 101 via the insulator 105. The bolts B2 areinserted and fixed in the bolt holes 858A and 858B of the housing 8. Thebolts B2 are inserted in the recessed portion 102 a of the second mountportion 102. The bolts B2 fix the front surface 801 of the housing 8 tothe second mount portion 102 via the insulators 108. The pin PIN and thebolts B2 are made from metal. The holes 858 and 859 function as afixation portion for fixing the housing 8 to the vehicle body side (themount 100). The insulators 105 and 108 are each an elastic member forpreventing or reducing (insulating) a vibration, and are made from arubber material.

The insulator 105 of the first mount portion 101 has a cylindricalshape, and includes a small-diameter portion 105 a and an annularstepped portion 105 b extending in a direction around a central axisthereof on one axial side of an outer peripheral surface. An innerdiameter of the insulator 105 is generally equal to an outer diameter ofthe pin PIN (a shaft portion thereof). The insulator 105 is fitted to anouter periphery of the pin PIN (the shaft portion thereof). Thesmall-diameter portion 105 a is fitted in the insulator hole of thefirst mount portion 101. The stepped portion 105 b is in contact with anouter peripheral edge of the insulator hole from the Z-axis positivedirection side. An axial end surface of the insulator 105 is in contactwith the bottom surface 803 of the housing 8 from the Z-axis negativedirection side. An elastic deformation of the insulator 105 allows aslight displacement of the pin PIN relative to the first mount portion101. The pin PIN is a structure supporting the housing 8 (the bottomsurface 803) and functions as a support portion of the bottom surface803.

FIG. 11 illustrates a cross section of the bolt B2 and the like attachedin the bolt hole 858A taken along a plane passing through a central axisof the bolt B2. FIG. 11 corresponds to a cross section as viewed from aline XI-XI illustrated in FIG. 10. The bolt B2 is fixed to the housing 8via a collar member 106 and a washer 107. The collar member 106 isformed into a cylindrical shape from a metallic material, and includes asmall-diameter portion 106 a and a large-diameter portion 106 b. Anouter diameter of the large-diameter portion 106 b is larger than anouter diameter of the small-diameter portion 106 a, and the outerdiameter of the small-diameter portion 106 a is generally equal to anouter diameter of a head portion B21 of the bolt B2. The washer 107 isformed into an annular plate-like shape from a metallic material, and anouter diameter thereof is larger than the outer diameter of the headportion B21. The insulators 108 of the second mount portion 102 eachhave a cylindrical shape, and include an annular groove 108 a extendingin a direction around a central axis at a generally central portion onan outer peripheral surface in the axial direction. An axial dimensionof the insulator 108 is generally equal to an axial dimension of thesmall-diameter portion 106 b. An inner diameter of the insulator 108 isgenerally equal to the outer diameter of the small-diameter portion 106a. The bolt B2, the collar member 106, and the washer 107 (they will behereinafter referred to as the bolt B2 and the like) are fixed to thehousing 8. A male screw on an distal end side of the above-describedshaft portion is threadably engaged with a female screw of the bolt hole858A with the shaft portion of the bolt B2 penetrating through thecollar member 106 and the washer 107. An axial end surface of thelarge-diameter portion 106 b is in contact with the front surface 801 ofthe housing 8, an axial end surface of the small-diameter portion 106 ais in contact with a surface of the washer 107 on one side, and asurface of the washer 107 on an opposite side is in contact with thehead portion B21 of the bolt B2. The insulator 108 is fitted to an outerperiphery of the small-diameter portion 106 a. The recessed portion 102a of the second mount portion 102 is fitted to the groove 108 a of theinsulator 108. An elastic deformation of the insulator 108 allows aslight displacement of the bolt B2 and the like relative to the secondmount portion 102. The bolt B2 and the like are a structure supportingthe housing 8 (the front surface 801), and function as a support portionof the front surface 801. A support portion of the second mount portion102 on the X-axis positive direction side is also configured in asimilar manner.

FIG. 12 is an exploded perspective view illustrating processes ofmounting the second unit 1B onto the mount 100. In a first process, theinsulator 105 is attached to the first mount portion 101, and theinsulators 108 and the collar members 106 are attached to the secondmount portion 102. The pin PIN is press-fitted in the bottom surface803. In a second process, the housing 8 is moved relative to the mounttoward the Z-axis negative direction side, and the pin PIN is insertedin the inner periphery of the insulator 105 as indicated by an arrow inFIG. 12. The bottom surface 803 is in contact with end surfaces of theinsulators 108 in the Z-axis positive direction. In a third process, theshaft portions of the bolts B2 are inserted in inner peripheries of thecollar members 106 as indicated by arrows in FIG. 12, and the distal endsides of the above-described shaft portions are inserted in the boltholes 858A and 858B, with the washers 107 attached to the bolts B2. Theshaft portions are threadably engaged with the bolt holes 858A and 858Bdue to rotations of the head portions B21 of the bolts B2. The collarmembers 106 are sandwiched between the head portions B21 (the washers107) and the front surface 801 and are fixed to the front surface 801with the aid of the axial forces of the bolts B2.

Next, functions will be described.

(Reduction in Pulse Pressure of Pump)

The pump 3 may be any pump including a member reciprocatable accordingto a motion of the cam, and a specific configuration thereof is notlimited to the example according to the present embodiment. In thepresent embodiment, the pump 3 includes the plurality of pump portions3A to 3E. A straight line defined by extending the central axis 360 ofthe arbitrary pump portion 3A or the like beyond the central axis O ofthe rotational driving shaft 300 has an angle larger than 0 degree inthe direction around the central axis O relative to the central axis 360of the other pump portion 3C, 3D, or the like. In other words, thecentral axes 360 of the two pump portions 3A and 3C or the like oppositeof the central axis O from each other are not located on the samestraight line, and form the angle larger than 0 degree. Therefore,respective intake/discharge strokes of the pump portions 3A to 3E arenot synchronized and out of phase with one another. This allows periodicchanges (pulse pressures) of respective discharge pressures of the pumpportions 3A to 3E to reduce each other, thereby succeeding in reducing apulse pressure as the entire pump 3. In other words, a change as largeas a sum of the discharge pressures of the plurality of pump portions 3Ato 3E can be reduced as the entire pump 3. The present embodiment canreduce noise and a vibration of the brake system 1 by reducing pulsationof the flow in the discharge fluid passage 13 into which each of thepump portions 3A to 3E discharges the brake fluid in common.

The plurality of plungers 36 is disposed at the generally even intervalsin the circumferential direction. In other words, each of the plungers36 is arrayed generally evenly in the circumferential direction.Therefore, the present embodiment can reduce the change as large as thesum of the discharge pressures of the plurality of pump portions 3A to3E as much as possible as the entire pump 3 by allowing the pumpportions 3A to 3E to have generally even phase shifts of theintake/discharge strokes among them. Therefore, the present embodimentcan acquire a further high effect of reducing the pulse pressure. Thenumber of pump portions 3A to 3E may be an even number. In the presentembodiment, the above-described number is an odd number equal to orlarger than three. Therefore, compared to when the above-describednumber is an even number, the present embodiment can easily reduce themagnitude of the pulse pressure (a width of the change) as the entirepump 3 by shifting the phases while disposing the plurality of pumpportions 3A to 3E at the generally even intervals in the circumferentialdirection, thereby noticeably acquiring the effect of reducing the pulsepressure. For example, in the case where the above-described number isthree, a higher effect of reducing the pulse pressure can be acquiredthan when the above-described number is six. The number of pump portions3A to 3E (the plungers 36) is not limited to five, and may be, forexample, three. In the present embodiment, the above-described number isfive. Therefore, compared to when the above-described number is three,the present embodiment can improve the effect of reducing the pulsepressure to thus acquire sufficient quietness, and can also ensure asufficient discharge amount as the entire pump 3 while preventing orcutting down an increase in the size of the second unit 1B by reducingthe size of each of the pump portions 3A to 3E. Further, compared towhen the above-described number is six or more, the present embodimentcuts down the increase in the number of pump portions 3A to 3E, andtherefore is advantageous in terms of a layout and the like and caneasily achieve a reduction in the size of the second unit 1B.

The number of pump portions 3C and 3D positioned on the vertically upperside with respect to the central axis O is two, and the number of pumpportions 3A, 3B, and 3E positioned on the vertically lower side withrespect to the central axis O is three. The number of pump portions onthe vertically lower side is larger than on the vertically upper side,which makes it easy to position a center of gravity of the second unit1B on the vertically lower side. Positioning the center of gravity ofthe second unit 1B on the vertically lower side can improve installationstability of the second unit 1B. At least single pump portion 3A amongthe pump portions 3A, 3B, and 3E positioned on the vertically lower sideis disposed from the bottom surface 803 into the housing 8. Therefore,the present embodiment facilitates disposing the pump portions 3A, 3B,and 3E at the generally even intervals in the direction around thecentral axis O on the vertically lower side compared to when the pumpportion is not disposed from the bottom surface 803. The pump portions3A, 3B, and 3E positioned on the vertically lower side are disposed fromthe bottom surface 803, the left side surface 805, and the right sidesurface 806 into the housing 8, respectively. Respectively assigning theopenings of the pump portions 3A, 3B, and 3E to these surfaces in thismanner further facilitates disposing the pump portions 3A, 3B, and 3E atthe generally even intervals in the direction around the central axis Oon the vertically lower side. The pump portion 3C, which is one of thepump portions 3C and 3D positioned on the vertically upper side, isdisposed from the first recessed portion 80A into the housing 8, and thepump portion 3D, which is the other of the pump portions 3C and 3Dpositioned on the vertically upper side, is disposed from the secondrecessed portion 80B into the housing 8. Respectively assigning theopenings of the pump portions 3C and 3D to the recessed portions 80A and80B in this manner facilitates disposing the pump portions 3A to 3E atthe generally even intervals in the direction around the central axis O.

(Reservoir Function)

The first fluid pool chamber 83 is replenished with the brake fluid fromthe reservoir tank 4 via the pipe 10R, and also functions as thereservoir (an internal reservoir) to supply the brake fluid to theintake port 823 of each of the pump portions 3A to 3E. Each of the pumpportions 3A to 3E introduces and discharges the brake fluid via thefirst fluid pool chamber 83. The first fluid pool chamber 83 has acylindrical shape, and a radial cross-sectional area thereof is largerthan a cross-sectional area of the flow passage of the intake fluidpassage 12 opened to the first fluid pool chamber 83. In other words,the first fluid pool chamber 83 is a volume chamber above the intakefluid passage 12. When the brake fluid leaks from the intake pipe 10Rdue to, for example, a detachment of the intake pipe 10R from the nipple10R1 or 10R2 or loosening of a band fastening the intake pipe 10R to thenipple 10R1 or 10R2, the first fluid pool chamber 83 functions as thereservoir storing the brake fluid therein. The pump 3 can generate thewheel cylinder hydraulic pressures and can generate a braking torque onthe vehicle on which the brake system 1 is mounted by introducing thebrake fluid from the first fluid pool chamber 83 and discharging thebrake fluid. When the fluid leaks from the intake pipe 10R, the presentembodiment can secure the brake fluid in the first chambers 43P and 43Salthough the brake fluid reduces in the second chamber 43R of thereservoir tank 4, thereby continuously realizing the pressing forcebrake.

The intake port 873 may be connected to the first fluid pool chamber 83via a fluid passage (having a smaller cross-sectional area of the flowpassage than the radial cross-sectional area of the first fluid poolchamber 83). In the present embodiment, the intake port 873 is directlyconnected to the first fluid pool chamber 83. In other words, the firstfluid pool chamber 83 is disposed from the top surface 804 into thehousing 8. The opening portion of the first fluid pool chamber 83functions as the intake port 873. Therefore, the present embodimentallows the first fluid pool chamber 83 to be disposed as close to thesurface (the top surface 804) side of the housing 8 as possible, therebysucceeding in securing a large substantial volume of the first fluidpool chamber 83. The first fluid pool chamber 83 is disposed on thevertically upper side with respect to the intake port 823 of each of thepump portions 3A to 3E. Therefore, the present embodiment allows thebrake fluid to be easily supplied from the first fluid pool chamber 83to the intake port 823 of each of the pump portions 3A to 3E via theintake fluid passage 12 with the aid of a weight of the brake fluiditself. Further, the present embodiment prevents or reduces retention ofair inside the intake fluid passage 12, thereby preventing or reducingan intake of air (air bubbles) by the pump 3. The intake port 873 doesnot have to be opened on the top surface 804, and may be opened on, forexample, the right side surface 806. In the present embodiment, theintake port 873 is opened on the top surface 804. Therefore, the firstfluid pool chamber 83 is disposed on the vertically upper side of thehousing 8, which facilitates disposing the first fluid pool chamber 83on the vertically upper side with respect to the intake port 823 of eachof the pump portions 3A to 3E.

(Drain Function)

The brake fluid leaks out from each of the cylinder containing holes 82to the cam containing hole 81 via the first seal ring 34. For example,the brake fluid leaks out from the intake-side space R1 by passingthrough the gap between the plunger 36 and the first seal ring 34. Thebrake fluid leaking out to the cam containing hole 81 is introduced intothe second fluid pool chamber 84 via the drain fluid passage 19 andstored in the chamber 84. Therefore, the present embodiment can preventor reduce entry of the brake fluid located in the cam containing hole 81into the motor 20, thereby succeeding in improving operability of themotor 20. The chamber 84 is disposed on the Z-axis negative directionside with respect to the cam containing hole 81. Therefore, the presentembodiment allows the brake fluid leaking out from each of the cylindercontaining holes 82 to the cam containing hole 81 to be transmitted fromthe cam containing hole 81 to the chamber 84 with the aid of the weightof the brake fluid itself. As a result, the present embodiment allowsthe above-described brake fluid leaking out to the chamber 84 to beefficiently stored. The chamber 84 is opened on the bottom surface 803,and is disposed from the bottom surface 803 into the housing 8.Therefore, the present embodiment allows the chamber 84 to be disposedas close to one side where the bottom surface 803 is located aspossible, thereby succeeding in securing a large substantial volume ofthe chamber 84. The opening of the chamber 84 is closed by a covermember 840. The cover member 840 may be provided in such a manner that aposition thereof in the Z-axis direction relative to the housing 8 (thebottom surface 803) is adjustable with use of, for example, a screw. Asa result, the present embodiment can change the substantial volume ofthe chamber 84.

(Size Reduction and Improvement of Layout Efficiency)

The brake system 1 includes the first unit 1A and the second unit 1B.Therefore, the present embodiment can improve mountability of the brakesystem 1 onto the vehicle. The stroke simulator 6 is disposed on thefirst unit 1A. Therefore, the present embodiment can reduce a length ofthe pipe connecting the master cylinder 5 or the second unit 1B and thestroke simulator 6 to each other and can also reduce the number of pipescompared when the stroke simulator 6 is a separate member from themaster cylinder 5 or the second unit 1B. Therefore, the presentembodiment can prevent or reduce complication of the brake system 1, andcan also prevent or cut down a cost increase accompanying the increasein the number of pipes. The stroke simulator 6 is disposed on the firstunit 1A, and the master cylinder 5 and the stroke simulator 6 areintegrated as the first unit 1A. Therefore, the present embodiment canprevent or cut down an increase in the size of the second unit 1Bcompared to when the stroke simulator 6 is disposed on the second unit1B. The pipe connecting the stroke simulator 6 and the second unit 1B toeach other does not include a pipe connecting the positive pressurechamber 601 and the second unit 1B to each other, and includes only thebackpressure pipe 10X connecting the backpressure chamber 602 and thesecond unit 1B to each other. Therefore, the present embodiment canreduce the number of pipes connecting the first unit 1A (the strokesimulator) and the second unit 1B to each other.

The electromagnetic valves, the hydraulic sensor 91, and the like aredisposed on the second unit 1B. Therefore, the present embodiment doesnot require an ECU for driving the electromagnetic valves on the firstunit 1A, and neither requires a wiring (a harness) for controlling theelectromagnetic valves and transmitting sensor signals between the firstunit 1A and the ECU 90 (the second unit 1B). Therefore, the presentembodiment can prevent or reduce the complication of the brake system 1,and can also prevent or cut down a cost increase accompanying anincrease in the number of pipes. Further, since no ECU is disposed onthe first unit 1A, the present embodiment can reduce a size of the firstunit 1A and improve layout flexibility thereof. For example, the SS/V IN27 and the like are disposed on the second unit 1B. Therefore, thepresent embodiment does not require an ECU for switching the activationof the stroke simulator 6 on the first unit 1A, and neither requires awiring (a harness) for controlling the SS/V IN 27 and the SS/V OUT 28between the first unit 1A and the ECU 90 (the second unit 1B). The ECU90 is attached to the housing 8, and the ECU 90 and the housing 8(containing the electromagnetic valves and the like) are integrated asthe second unit 1B. Therefore, the present embodiment can omit a wiring(a harness) connecting the electromagnetic valves, the hydraulic sensor91, and the like, and the ECU 90 to each other. More specifically, theterminals of the solenoids of the electromagnetic valves 21 and thelike, and the terminals of the hydraulic sensor 91 and the like aredirectly connected to the control board (without intervention of aharness and a connector outside the housing 8). Therefore, for example,the present embodiment can omit a harness connecting the ECU 90 and theSS/V IN 27 and the like to each other. The motor 20 is disposed on thefirst unit 1B, and the housing 8 (containing the pump 3 therein) and themotor 20 are integrated as the second unit 1B. This second unit 1Bfunctions as a pump apparatus. Therefore, the present embodiment canomit a wiring (a harness) connecting the motor 20 and the ECU 90 to eachother. More specifically, the conductive member for supplying power andtransmitting signals to the motor 20 is contained in the power sourcehole 86 of the housing 8, and is directly connected to the control board(without intervention of a harness and a connector outside the housing8). The conductive member functions as the connection member connectingthe control board and the motor 20 to each other.

The housing 8 is sandwiched between the motor 20 and the ECU 90. Inother words, the motor 20, the housing 8, and the ECU 90 are disposed soas to be arranged in this order along the axial direction of the motor20. More specifically, the ECU 90 is attached to the back surface 802opposite from the front surface 901 to which the motor 20 is attached.Therefore, the motor 20 and the ECU 90 can be disposed so as to overlapeach other as viewed from one side where the motor 20 is located or theother side where the ECU 90 is located (as viewed from the Z-axisdirection). As a result, the present embodiment can reduce the area ofthe second unit 1B as viewed from the one side where the motor 20 islocated or the other side where the ECU 90 is located, therebysucceeding in a reduction in the size of the second unit 1B. The presentembodiment can achieve a reduction in a weight of the second unit 1B dueto the reduction in the size of the second unit 1B.

The connector portion 903 of the ECU 90 is adjacent to the housing 8(the left side surface 905) as viewed from the Z-axis positive directionside. In other words, the connector portion 903 is not covered by thehousing 8 and protrudes from the left side surface 805 of the housing 8as viewed from the one side where the motor 20 is located. Therefore,the control board of the ECU 90 can be extended to not only a regionoverlapping the housing 8 but also a region overlapping the connectorportion 903 (a region adjacent to the left side surface 805) as viewedfrom the one side where the motor 20 is located. The bolts b2 forattaching the ECU 90 to the back surface 802 are not fixed to thehousing 8 by penetrating through the ECU 90 from the other side wherethe back surface 802 (the ECU 90) is located but are fixed bypenetrating through the housing 8 from the one side where the frontsurface 801 is located. If the bolts b2 penetrate through the ECU 90(the control board), the control board would be unable to be disposed ata portion through which these bolts b2 penetrate. Further, if thecontrol board is also disposed on a back of the connector portion 903,the control board would be unable to be disposed in proximity to theportion through which the bolts b2 penetrate. The incapability todispose the control board makes it impossible to lay a wiring patternand mount an element at this portion. In other words, an area where thecontrol board is implemented reduces. Providing the bolts b2 so as topenetrate through the housing 8 without penetrating through the ECU 90can eliminate a portion where the bolts b2 and the control board wouldotherwise interfere with each other. Therefore, the present embodimentcan secure a wide area where the control board is implemented, andeasily deal with multi-functionalization of the ECU 90.

The terminal of the connector portion 903 extends in the Y-axisdirection. Therefore, the present embodiment can prevent or cut down anincrease in a dimension of the second unit 1B as viewed from the Y-axisdirection (in the X-axis direction). The terminal of the connectorportion 903 is exposed toward the one side where the motor 20 is located(the Y-axis positive direction side). Therefore, the connector (theharness) connected to the connector portion 903 overlaps the housing 8and the like in the axial direction of the motor 20 (the Y-axisdirection), whereby the present embodiment can prevent or cut down anincrease in a dimension of the second unit 1B including this connector(the harness) in the Y-axis direction (the axial direction of the motor20). The connector portion 903 is adjacent to the left side surface 805of the housing 8. Therefore, the present embodiment can prevent orreduce interference between the connector (the harness) connected to theconnector portion 903 and the pipes 10M and 10W respectively connectedto the ports 871 and 872 compared when the connector portion 903 isadjacent to the top surface 904 of the housing 8. Further, the presentembodiment can prevent or reduce interference between the vehiclebody-side member (the mount 100) that the bottom surface 803 faces andthe above-described connector (the harness) compared to when theconnector portion 903 is adjacent to the bottom surface 803 of thehousing 8. The rotational driving shaft 300 extends in the horizontaldirection (y-axis direction) in the state mounted on the vehicle.Therefore, the connector portion 903 extends in the horizontal directionin the state mounted on the vehicle. As a result, the present embodimentcan prevent or reduce entry of water into the connector portion 903while securing connectivity of the harness to the connector portion 903.The connector portion 903 may be adjacent to the right side surface 806of the housing 8. In the present embodiment, the connector portion 903is adjacent to the left side surface 805. A port or the like, such asthe backpressure port 874, is not formed on the left side surface 805.Therefore, the present embodiment can prevent or reduce interferencebetween the connector (the harness) connected to the connector portion903 and the pipe 10X connected to the backpressure port 874 compared towhen the connector portion 903 is adjacent to the right side surface806. In other words, when the connector (the harness) is connected tothe connector portion 903, the present embodiment facilitates theconnection thereof. Therefore, the present embodiment can improvemounting workability of the brake system 1 onto the vehicle.

The plurality of pump portions 3A to 3E overlap one another in the axialdirection of the rotational driving shaft 300. The cylinder containingholes 82A to 82E are arrayed in one row along the axial direction of themotor 20. More specifically, the central axes 360 of the cylindercontaining holes 82A to 82E are located on the generally same plane αgenerally orthogonal to the central axis O. Therefore, the presentembodiment can allow the cam unit 30 to be used by the plurality ofplungers 36 in common to thus prevent or cut down an increase in thenumber of cam units 30, thereby preventing or cutting down increases inthe number of parts and the cost. Further, the present embodiment canshorten the rotational driving shaft 300 to prevent or cut down anincrease in a dimension of the housing 8 in the axial direction of themotor 20 by preventing or cutting down the increase in the number of camunits 30. As a result, the present embodiment can achieve reductions inthe size and the weight of the second unit 1B. Further, the presentembodiment can further effectively prevent or cut down the increase inthe dimension of the housing 8 in the axial direction of the motor 20 bymaximizing a range where the individual cylinder containing holes 82A to82E overlap one another in the Y-axis direction. The cylinder containingholes 82 are disposed on the front surface 801 side of the housing 8(the one side where the motor 20 is mounted). Therefore, the presentembodiment can further shorten the rotational driving shaft 300.Further, the present embodiment can simplify a layout of the fluidpassages due to the plurality of pump portions 3A to 3E overlapping oneanother in the axial direction of the rotational driving shaft 300.Therefore, the present embodiment can prevent or cut down the increasein the size of the housing 8.

The housing 8 includes the plurality of cylinder containing holes 82containing the plungers 36 of the pump 3 therein, and the plurality ofvalve containing holes containing the valve bodies of theelectromagnetic valves 21 and the like therein. These cylindercontaining holes 82 and the valve containing holes at least partiallyoverlap each other as viewed from the Y-axis direction. Therefore, thepresent embodiment can reduce the area of the second unit 1B as viewedfrom the one side where the motor 20 is located. The plurality ofcylinder containing holes 82 is provided radially around the centralaxis O of the motor 20. Therefore, the present embodiment facilitatesprovision of the region where the individual cylinder containing holes82A to 82E overlap one another in the axial direction of the motor 20.Most of the plurality of valve containing holes is contained in thecircle connecting the ends of the cylinder containing holes 82 on thelarge-diameter portion 821 side (the other side farer away from thecentral axis O) as viewed from the Y-axis direction. Alternatively, theouter periphery of this circle and the valve containing holes at leastpartially overlap each other. Therefore, the present embodiment canreduce the area of the second unit 1B as viewed from the Y-axisdirection.

The plurality of valve containing holes is arrayed in one row along theaxial direction of the motor 20. Therefore, the present embodiment canprevent or cut down the increase in the dimension of the housing 8 inthe axial direction of the motor 20. The valve containing holes aredisposed on the other side of the housing 8 where the back surface 802is located (the other side where the ECU 90 is attached). Therefore, thepresent embodiment can improve electric connectivity between the ECU 90and the solenoids of the electromagnetic valves 21 and the like. Morespecifically, the central axes of the plurality of valve containingholes extend generally in parallel with the central axis of the motor20, and all the valve containing holes are opened on the back surface802. Therefore, the present embodiment allows the solenoids of theelectromagnetic valves 21 and the like to be concentrated on the backsurface 802 of the housing 8, thereby succeeding in simplification ofthe electric connections between the ECU 90 and the solenoids.Similarly, the plurality of sensor containing holes is disposed on theback surface 802 side. Therefore, the present embodiment can improveelectric connectivity between the ECU 90 and the hydraulic sensor 91 andthe like. The control board of the ECU 90 is disposed generally inparallel with the back surface 802. Therefore, the present embodimentcan simplify the electric connection between the ECU 90 and thesolenoids (and the sensors).

The housing 8 includes a pump region (a pump portion) and anelectromagnetic valve region (an electromagnetic valve portion) in thisorder from the front surface 801 side to the back surface 802 side alongthe axial direction of the motor 20. The region where the cylindercontaining holes 82 are positioned is the pump region and the regionwhere the valve containing holes are positioned is the electromagneticvalve region along the axial direction of the motor 20. The presentembodiment can easily prevent or cut down the increase in the dimensionof the housing 8 in the axial direction of the motor 20 by concentratingthe cylinder containing holes 82 and the valve containing holes for eachof the regions in the axial direction of the motor 20 in this manner.Further, the present embodiment can improve the layout efficiency ofeach of the elements of the housing 8 and achieve the reduction in thesize of the housing 8. In other words, the present embodiment increasesthe layout flexibility of the plurality of holes in the plane orthogonalto the central axis of the motor 20 in each of the regions. For example,the present embodiment facilitates disposing the plurality of valvecontaining holes in the electromagnetic valve region so as to prevent orcut down the increase in the dimension of the housing 8 in theabove-described plane. These regions may partially overlap each other inthe axial direction of the motor 20.

The recessed portions 80A and 80B are formed at the corner portions onthe one side and the other side of the housing 8 where the front surface801 and the top surface 804 are located, respectively. Therefore, theone side and the other side of the housing 8 where the front surface 801and the top surface 804 are located, respectively, are reduced in volumeand thus reduced in weight by amounts corresponding to the recessedportions 80A and 80B. In this manner, the present embodiment can reducethe volume and the weight of the housing 8. The two cylinder containingholes 82C and 82D on the Z-axis positive direction side are disposed onboth the opposite sides of the central axis O from each other in theX-axis direction. Therefore, the cylinder containing holes 82 are notopened in the vicinity of the central axis O (the center in the X-axisdirection) on the top surface 804, whereby the present embodiment canprepare a large space where the other hole (the first fluid pool chamber83) is opened. The wheel cylinder ports 872 are opened on the topsurface 804. Therefore, the present embodiment can save the space of thefront surface 801 and facilitate the formation of the recessed portions80A and 80B at the corner portions of the housing 8 compared to when theports 872 are opened on the front surface 801. The ports 872 aredisposed on the Y-axis negative direction side of the top surface 804.Therefore, the present embodiment can facilitate the connection betweenthe ports 872 and the SOL/V IN containing holes and the like whileavoiding interference between the ports 872 and the cylinder containingholes 82, thereby simplifying the fluid passages, by disposing the ports872 in the electromagnetic valve region. The four ports 872 are disposedso as to be arranged in the X-axis direction on the Y-axis negativedirection side of the top surface 804. Therefore, the present embodimentcan prevent or cut down the increase in the dimension of the housing 8in the Y-axis direction by arranging the ports 872 in one row in theY-axis direction.

The master cylinder ports 871 are opened on the front surface 801.Therefore, the present embodiment can save the space of the top surface804 and facilitate the formation of the wheel cylinder ports 872 and thelike on the top surface 804 compared to when the ports 871 are opened onthe top surface 804. The ports 871 are disposed on the Z-axis positivedirection side of the front surface 801 with respect to the central axisO. The ports 871 are located on the Z-axis positive direction side withrespect to the motor housing 200, and overlap the motor housing 200 inthe X-axis direction (as viewed from the Z-axis direction). Therefore,the present embodiment can prevent or cut down an increase in adimension of the front surface 801 in the X-axis direction. The ports871P and 871S sandwich the first fluid pool chamber 83 in the X-axisdirection (as viewed from the Y-axis direction). In other words, thefirst fluid pool chamber 83 is disposed between the ports 871P and 871Sin the X-axis direction. The present embodiment can improve the layoutefficiency inside the housing 8 and can also reduce the area of thefront surface 801, thereby achieving the reduction in the size of thehousing 8, by utilizing the space between the ports 871P and 871S toform the first fluid pool chamber 83 in this manner. The individualports 871P and 871S are sandwiched between the first fluid pool chamber83 and the cylinder containing holes 82C and 82D, respectively, in thedirection around the central axis O (as viewed from the Y-axisdirection). Therefore, the present embodiment can prevent or cut down anincrease in a dimension from the central axis O to the outer surface(the top surface 804) of the housing 8, thereby achieving the reductionin the size of the housing 8. Further, the present embodiment allows theopening portions of the ports 871 on the front surface 801 to bedisposed on the central side in the X-axis direction, therebyfacilitating the formation of the recessed portions 80A and 80B outsidethe ports 871P and 871S in the X-axis direction.

The backpressure port 874 is opened on the right side surface 806.Therefore, the present embodiment can save the space of the frontsurface 801 or the top surface 804 compared to when the port 874 isopened on the front surface 801 or the top surface 804. Therefore, thepresent embodiment can prevent or cut down the increase in the area ofthe front surface 801 or the top surface 804, thereby preventing orcutting down the increase in the size of the housing 8. The port 874 isopened on the right side surface 806. The connector portion 903 is notadjacent to the right side surface 806. Therefore, the presentembodiment can prevent or reduce the interference between the connector(the harness) connected to the connector portion 903 and the pipe 10Xconnected to the port 874 compared to when the port 874 is adjacent tothe left side surface 805. In other words, when the pipe 10X isconnected to the port 874, the present embodiment facilitates theconnection thereof. Therefore, the present embodiment can improve themounting workability of the brake system 1 onto the vehicle.

The intake port 873 is opened on the Y-axis positive direction side (thepump region) on the top surface 804. Therefore, the present embodimentfacilitates the connection of the cylinder containing holes 82 (theintake ports 823 of the pump portions 3C and 3D) to the port 873 (thefirst fluid pool camber 83), thereby succeeding in simplifying the fluidpassages. The port 873 is opened on the central side in the X-axisdirection on the top surface 804. Therefore, in the case where thesingle first fluid pool chamber 83 is used for both the P and S systemsin common, the present embodiment facilitates the connection of the port873 (the chamber 83) to the valve containing holes of both the systems,thereby succeeding in simplifying the fluid passages. The wheel cylinderports 872 c and 872 d sandwich the intake port 873 (the first fluid poolchamber 83), and the openings of the ports 872 c and 872 d and theintake port 873 (the first fluid pool chamber 83) partially overlap eachother in the X-axis direction (as viewed from the Y-axis direction).Therefore, the present embodiment can prevent or cut down the increasein the dimension of the housing 8 in the X-axis direction, therebyachieving the reduction in the size.

The first fluid pool chamber 83 is opened on the outer surface of thehousing 8. More specifically, a radial cross section of the first fluidpool chamber 83 is opened on the surface (the top surface 804) of thehousing 8. Therefore, the present embodiment eliminates the necessity ofa thickness around the first fluid pool chamber 83 (especially on thesurface side of the housing 8 in the axial direction of the first fluidpool chamber 83) compared to when the first fluid pool chamber 83 isconnected to the intake port 873 (the top surface 804) via the fluidpassage (having a smaller cross-sectional area of the fluid passage thana radial cross-sectional area of the first fluid pool chamber 83). As aresult, the present embodiment can improve the layout efficiency (volumeefficiency) inside the housing 8. Further, the present embodimentsimplifies handling of the fluid passage from the intake port 873 (thetop surface 804) to the first fluid pool chamber 83. Therefore, thepresent embodiment can facilitate processing of the housing 8 and alsoachieve the reduction in the size of the housing 8. The intake port 873does not have to be opened on the top surface 804. For example, with thecentral axis of the first fluid pool chamber 83 extending in the Y-axisdirection and the first fluid pool chamber 83 opened on the frontsurface 801 on the Y-axis positive direction side, this opening portionmay function as the intake port 873. In the present embodiment, with thecentral axis of the first fluid pool chamber 83 extending in thedirection orthogonal to the central axis O and the first fluid poolchamber 83 opened on the outer surface (the top surface 804) of thehousing 8 intersecting with this direction (extending along thedirection around the central axis O), this opening portion functions asthe intake port 873. Therefore, the present embodiment can prevent orcut down the increase in the dimension from the central axis O to theouter surface (the top surface 804 on which the first fluid pool chamber83 is opened) of the housing 8 extending along the direction around thecentral axis O, thereby succeeding in the reduction in the size of thehousing 8.

The first fluid pool chamber 83 is formed in the region between thecylinder containing holes 82C and 82D adjacent to each other in thedirection around the central axis O. Therefore, the present embodimentcan shorten the intake fluid passage 12 connecting the chamber 83 andthe intake ports 823 of the pump portions 3C and 3D to each other.Further, the present embodiment can prevent or cut down an increase in adimension from the central axis O to the outer surface (the top surface804 on which the chamber 83 is opened) of the housing 8 extending alongthe direction around the central axis O, thereby achieving the reductionin the size of the housing 8, by disposing the chamber 83 closer to thecentral axis O. In other words, the present embodiment can improve thelayout efficiency (the volume efficiency) inside the housing 8 and canalso reduce the area of the front surface 801, thereby achieving thereduction in the size of the housing 8, by utilizing the space betweenthe holes 82C and 82D to form the chamber 83. The present embodiment canreduce the space between the chamber 83 (the bottom portion thereof) andthe hole 81, thereby improving the above-described layout efficiency, bydisposing the chamber 83 closer to the cam containing hole 81. The powersource hole 86 is formed in the region between the holes 82C and 82Dadjacent to each other in the direction around the central axis O.Therefore, the present embodiment can improve the layout efficiency (thevolume efficiency) inside the housing 8 and can also reduce the area ofthe front surface 801, thereby achieving the reduction in the size ofthe housing 8, by utilizing the space between the holes 82C and 82D toform the power source hole 86. The present embodiment can furtherimprove the above-described layout efficiency by disposing the spacebetween the hole 86 and the hole 81 of the chamber 83 (the bottomportion thereof). The holes 82C and 82D and the chamber 83 partiallyoverlap each other in the Y-axis direction (as viewed from the X-axisdirection). Therefore, the present embodiment can prevent or cut downthe increase in the dimension of the housing 8 in the Y-axis direction,thereby achieving the reduction in the size. The chamber 83 is disposedin the region surrounded by the master cylinder ports 871P and 871S andthe wheel cylinder ports 872 c and 872 d. More specifically, the chamber83 overlaps each of the above-described port 871P and the like in theZ-axis direction, and is also located inside a quadrilateral defined byconnecting the above-described port 871P and the like with line segmentsas viewed from the Z-axis direction. The present embodiment can improvethe layout efficiency inside the housing 8 and can also achieve thereduction in the size of the housing 8, by utilizing the space betweenthe above-described port 871P and the like to form the chamber 83 inthis manner.

The second fluid pool chamber 84 does not have to be opened on thebottom surface 803. For example, the central axis of the chamber 84 mayextend in the Y-axis direction, and the chamber 84 may be opened on thefront surface 801 on the Y-axis positive direction side. In the presentembodiment, the central axis of the chamber 84 extends in the directionorthogonal to the central axis O, and the chamber 84 is opened on theouter surface (the bottom surface 803) of the housing 8 intersectingwith this direction (extending along the direction around the centralaxis O). Therefore, the present embodiment can prevent or cut down theincrease in the dimension from the central axis O to the outer surface(the bottom surface 803 on which the chamber 84 is opened) of thehousing 8 extending along the direction around the central axis O,thereby achieving the reduction in the size of the housing 8. Thechamber 84 is formed in the region between the cylinder containing holes82B and 82C adjacent to each other in the direction around the centralaxis O. Therefore, the present embodiment can prevent or cut down theincrease in the dimension from the central axis O to the outer surface(the bottom surface 803 on which the chamber 84 is opened) of thehousing 8 extending along the direction around the central axis O,thereby achieving the reduction in the size of the housing 8, bydisposing the chamber 84 closer to the central axis O. In other words,the present embodiment can improve the layout efficiency (the volumeefficiency) inside the housing 8 and can also reduce the area of thefront surface 801, thereby achieving the reduction in the size of thehousing 8, by utilizing the space between the holes 82B and 82C to formthe chamber 84. The present embodiment can reduce the space between thechamber 84 (the bottom portion thereof) and the hole 81, therebyimproving the above-described layout efficiency, by disposing thechamber 84 closer to the cam containing hole 81. The holes 82A to 82Eand the chamber 84 partially overlap each other in the Y-axis direction(as viewed from the X-axis direction). Therefore, the present embodimentcan prevent or cut down the increase in the dimension of the housing 8in the Y-axis direction, thereby achieving the reduction in the size.The chamber 84 is opened on the Y-axis positive direction side on thebottom surface 803. Therefore, the present embodiment can facilitate theconnection of the chamber 84 to the region in the cam containing hole 81where the holes 82A to 82E are opened, thereby simplifying the drainfluid passage 19.

The bolt holes 858A and 858B are disposed on the front surface 801 onthe Z-axis negative direction side with respect to the central axis O.The holes 858A and 858B are fixed with use of the bolts B2, and thecollar member 106 and the insulators 108 are attached around the boltsB2. These insulators 108 and the like overlap the motor housing 200 inthe X-axis direction and the Z-axis direction (as viewed from the Y-axisdirection). Therefore, the present embodiment can efficiently utilizethe space on the front surface 801 on the Z-axis negative direction sidewith respect to the central axis O, thereby preventing or cutting downthe increases in the dimensions of the front surface 801 in the X-axisdirection and the Z-axis direction. Further, the holes 858A and 858B aredisposed on the front surface 801 on the Z-axis negative direction sidewith respect to the central axis O, whereby the present embodiment canreduce the size of the second mount portion 102, which is an arm portionof the mount 100, thereby improving the mountability of the second unit1B.

(Improvement of Supportability and Prevention or Reduction of Vibration)

The center of gravity of the second unit 1B is slightly offset from thecenter of gravity of the housing 8 to one side where the connectorportion 903 is located (to the X-axis negative direction side) in theX-axis direction due to the provision of the connector portion 903. Thecenter of gravity of the second unit 1B is offset from the centralgravity of the housing 8 to the one side where the motor 20 is located(to the Y-axis positive direction side) in the Y-axis direction due tothe provision of the motor 20. The center of gravity of the second unit1B is offset from the center of gravity of the housing 8 to thevertically lower side (to the Z-axis positive direction side) in theZ-axis direction because, for example, the central axis O of therotational driving shaft 300 is provided on the Z-axis negativedirection side with respect to the center of the housing 8 in the Z-axisdirection, and, further, the number of pump portions 3A, 3B, and 3Epositioned on the Z-axis negative direction side is larger than thenumber of pump portions 3C and 3D positioned on the Z-axis positivedirection side with respect to the central axis O.

The housing 8 (the second unit 1B) is fixed to the vehicle body side viathe mount 100. Therefore, the present embodiment can improvesupportability of the structure supporting the housing 8. The secondunit 1B can be stably held by supporting the bottom surface 803 and thefront surface 801 of the housing 8 in the following manner. The supportportion of the bottom surface 803 and the support portion of the frontsurface 801 support the housing 8 in directions different from eachother, whereby the present embodiment can improve support strength withrespect to a load possibly applied to the housing 8 in multipledirections. More specifically, the pin hole 859 for the fixation to themount 100 is provided on the bottom surface 803 of the housing 8. Thepin hole 859 is opened on the bottom surface 803 and extends vertically.The pin PIN fixed in the hole 859, and the insulator 105 attached to thepin PIN also extend vertically. Therefore, the insulator 105 receivesthe weight of the second unit 1B (a load due to a gravitational forceapplied vertically downward) in the axial direction thereof andefficiently supports this vertical load, whereby the present embodimentcan stably support the second unit 1B with respect to the vehicle bodyside (the mount 100). Preferably, rubber highly resistant to axialcompression is used for the insulator 105. The bolt holes 858A and 858Bfor the fixation to the mount 100 are provided on the vertically lowerside on the front surface 801 of the housing 8 with respect to thecentral axis O. The holes 858A and 858B are opened on the front surface801, and extend horizontally. The bolts B2 fixed in the holes 858A and858B and the insulators 108 attached to the bolts B2 also extendhorizontally. The center of gravity of the second unit 1B is offset fromthe center of gravity of the housing 8 to the one side where the frontsurface 801 is located. The second unit 1B tends to be tilted to the oneside where the front surface 801 is located due to the weight of themotor 20. The insulators 108 receive, in the axial direction thereof,the load of the second unit 1B that is applied in a direction of theabove-described tilt, and efficiently support this horizontal load,whereby the present embodiment can stably support the second unit 1Bwith respect to the vehicle body side (the mount 100). Preferably,rubber highly resistant to axial compression is used for the insulators108. The center of gravity of the second unit 1B is positioned on thevertically lower side, whereby the present embodiment can improveinstallation stability of the second unit 1B. The first recessed portion80A and the second recessed portion 80B are opened on the top surface804. One side of the housing 8 where the top surface 804 is located isreduced in weight by the amount corresponding to the recessed portions80A and 80B. Therefore, the present embodiment can allow the center ofgravity of the second unit 1B to be easily positioned on the verticallylower side.

The two bolt holes 858A and 858B are opened on the front surface 801.Therefore, the present embodiment can further stably support the secondunit 1B by supporting the housing 8 on two points. Further, the presentembodiment can reduce a load applied to around each of the holes 858Aand 858B by supporting the load of the second unit 1B while furtherdistributing it to the two holes 858A and 858B (the bolts B2). Thepresent embodiment can reduce a dimension of each of the holes 858A and858B, thereby achieving the reduction in the size of the housing 8. Theholes 858A and 858B are disposed on the front surface 801 on both theopposite sides of the central axis O from each other in the X-axisdirection. The center of gravity of the second unit 1B is positionednear the central axis O in the X-axis direction. Therefore, the presentembodiment can further stably support the second unit 1B by fixing thehousing 8 on the opposite sides of the above-described center of gravityfrom each other in the X-axis direction. The holes 858A and 858B aredisposed at the ends of the front surface 801 on the both sides in theX-axis direction. Therefore, the present embodiment can further stablysupport the second unit 1B by increasing a distance between the twosupport points. Further, the present embodiment can further reduce theloads applied to around the holes 858A and 858B by increasing distancesfrom the center of gravity of the second unit 1B to the holes 858A and858B in the X-axis direction. The hole 859 is disposed on the Y-axisnegative direction side of the bottom surface 803. Therefore, thepresent embodiment can further stably support the second unit 1B byincreasing a distance between the support portion of the front surface801 (the portion where the front surface 801 is attached to the secondmount portion 102) and the support portion of the bottom surface 803(the portion where the bottom surface 803 is attached to the first mountportion 101).

The rotational force of the motor 20 is applied to the motor housing 200and the housing 8 as a reaction force via the motor rotational shaft andthe bearing of the rotational driving shaft 300. Due to this reactionforce, a vibration can occur in the second unit 1B in the directionaround the central axis O when the motor 20 (the pump 3) is activated.Further, in each of the pump portions 3A to 3E, the plunger 36reciprocates in the axial direction of each of the pump portions 3A to3E. The pump portions 3A to 3E become a source from which the vibrationof the housing 8 is generated (a vibration generation source). Thenumber of pump portions 3A, 3B, and 3E positioned on the verticallylower side with respect to the central axis O (three) is larger than thenumber of pump portions 3C and 3D positioned on the vertically upperside with respect to the central axis O of the rotational driving shaft300 (two) with the housing 8 mounted on the vehicle. Therefore, thevibration easily increases on the vertically lower side of the secondunit 1B. The above-described vibration can be transmitted from thesecond unit 1B to the vehicle body side via the mount 100. Further, thevibration of the second unit 1B can be transmitted to the first unit 1Avia the metallic pipes 10M and 10X and further transmitted to the dashpanel on the vehicle body side via the flange portion 78. Thetransmission of the vibration to the dash panel may cause occurrence ofnoise in the vehicle compartment. Further, in a case where a sensor fordetecting the motion state of the vehicle (for example, the angularspeed sensor, hereinafter referred to as a behavior sensor) is mountedinside the ECU 90 (the control board), the behavior sensor mayincorrectly detect the above-described vibration of the second unit 1Bas a motion of the vehicle body (for example, a yaw rate), so thatdetection accuracy of the behavior sensor may be deteriorated.

In the present embodiment, the housing 8 is supported on the verticallylower side with respect to the central axis O in the state mounted onthe vehicle. Therefore, a larger number of pump portions (three: 3A, 3B,and 3E) among the pump portions 3A to 3E, which are the vibrationgeneration source, are located closer to the support portion of thehousing 8. In other words, the housing 8 is supported in a region wherethe vibration easily increases. Therefore, the present embodiment moreeffectively prevent or reduce the vibration of the second unit 1B thanwhen the housing 8 is supported in a region where the vibration does noteasily increase. Further, the first and second recessed portions 80A and80B are opened on the top surface 804. The one side of the housing 8where the top surface 804 is located is reduced in weight by the amountcorresponding to the recessed portions 80A and 80B. The one side of thehousing 8 where the top surface 804 is located is the vertically upperside with respect to the central axis O and is not supported by thesupport portion. The portion where the housing 8 is not supported isreduced in weight in this manner, which prevents or reduces thevibration of the second unit 1B. Along with the success in preventing orreducing the above-described vibration of the second unit 1B, thepresent embodiment can reduce the vibration to be transmitted to thevehicle body side via the mount 100, thereby achieving the quietness inthe vehicle compartment. The housing 8 (the second unit 1B) is supportedon the vehicle body side (the mount 100) via the insulators 105 and 108.The insulators 105 and 108 absorb the above-described vibration that hasoccurred along with the activation of the second unit 1B. As a result,the present embodiment can further effectively prevent or reduce thetransmission of the above-described vibration from the second unit 1B tothe vehicle body side via the mount 100. Further, along with theprevention or reduction of the above-described vibration of the secondunit 1B, the present embodiment can reduce the vibration to betransmitted to the vehicle body side via the first unit 1A (the flangeportion 78), thereby achieving the quietness in the vehicle compartment.Further, even in the case where the behavior sensor is mounted on thecontrol board, the present embodiment can prevent or reduce thedeterioration of the detection accuracy of the behavior sensor due tothe prevention or reduction of the above-described vibration of thesecond unit 1B.

The pin hole 859 is opened on the bottom surface 803, and extendsvertically. The bolt holes 858A and 858B are opened on the front surface801, and extend horizontally. The support portion on the bottom surface803 and the support portion on the front surface 801 support the housing8 in the different directions from each other, whereby the presentembodiment can improve the effect of preventing or reducing thevibration with respect to the vibration that can occur in the housing 8in the multiple directions. The two bolt holes 858A and 858B are openedon the front surface 801. The housing 8 is supported at the two portionson the vertically lower side at least on the front surface 801, andtherefore is supported with improved strength compared to when thehousing 8 is supported at one portion on the vertically lower side. Thehousing 8 (the front surface 801) is supported at a plurality ofpositions in the region where the vibration easily increases, whicheffectively prevents or reduces the vibration of the second unit 1B.Further, the housing 8 is supported at the plurality of positions somedistance away from one another in the direction around the central axisO, which effectively prevents or reduces the vibration of the secondunit 1B in the direction around the central axis O. Further, the presentembodiment can reduce the size of each of the insulators 105 by furtherdistributing the vibration of the second unit 1B to the two insulators105 to absorb it, thereby improving the mountability of the second unit1B. The holes 858A and 858B are disposed on both the opposite sides ofthe central axis O from each other in the X-axis direction on the frontsurface 801. Therefore, the present embodiment can further effectivelyreduce the vibration around the central axis O of the second unit 1B bysupporting the housing 8 on the opposite sides of the central axis Ofrom each other in the X-axis direction. The holes 858A and 858B aredisposed on the ends of the front surface 801 on the both sides in theX-axis direction. Therefore, the present embodiment can furthereffectively reduce the vibration of the second unit 1B by increasing thedistance between the support points. The hole 859 is disposed on theY-axis negative direction side of the bottom surface 803. Therefore, thepresent embodiment can further effectively reduce the vibration of thesecond unit 1B by increasing the distance between the support portion ofthe front surface 801 (the portion where the front surface 801 isattached to the second mount portion 102) and the support portion of thebottom surface 803 (the portion where the bottom surface 803 is attachedto the first mount portion 101).

(Improvement of Workability)

The master cylinder ports 871 and the wheel cylinder ports 872 aredisposed on the vertically upper side of the housing 8. Therefore, thepresent embodiment can improve the workability when the pipes 10MP,10MS, and 10W are respectively attached to the ports 871 and 872 of thehousing 8 that are set on the vehicle body side. The wheel cylinderports 872 are opened on the top surface 804. Therefore, the presentembodiment can further improve the above-described workability. Themaster cylinder ports 871 are opened on the end of the front surface 801on the vertically upper side. Therefore, the present embodiment canfurther improve the above-described workability. Further, the intakeport 873 in communication with the first fluid pool chamber 83 isdisposed on the top surface 804, whereby the present embodimentfacilitates the handling of the pipe connected to the intake port 873.Further, the present embodiment facilitates work from above at the timeof the mounting onto the vehicle.

The ports 871 for connecting the master cylinder pipes 10M are locatedon the front surface 801. When each of the pipes 10M is fixed to theport 871, a nut is fastened with use of a tool. The tool approaches thefront surface 801. If a part of the bolt b2 for attaching the ECU 90 tothe back surface 802 protrudes into the front surface 801, this makes itdifficult to fasten the nut with use of the tool. In the presentembodiment, a part (the head portion) of the bolt b2 protrudes into eachof the first recessed portion 80A and the second recessed portion 80B.In other words, the part of the bolt b2 does not protrude into the frontsurface 801 except for the recessed portions 80A and 80B. Therefore,interference between the part of the bolt b2 and the tool is preventedor reduced, whereby the present embodiment facilitates work of fixingthe pipes 10M to the ports 871 with use of the tool. The cylindercontaining holes 82C and 82D are opened to the recessed portions 80A and80B, respectively. Therefore, the present embodiment can prevent or cutdown increases in axial dimensions of the holes 82C and 82D, therebyimproving efficiency of attaching the pump components into the holes 82Cand 82D.

Advantageous Effects

In the following description, advantageous effects of the presentembodiment will be listed.

(1) The second unit 1B (a hydraulic control apparatus) includes thehousing 8 including the fluid passages 11 and the like provided thereinand configured to be mounted on the vehicle, the rotational drivingshaft 300 provided inside the housing 8, and the plurality of pumpportions 3A to 3E (a plurality of plunger pumps) configured to beactivated by the rotation of the rotational driving shaft 300 anddisposed in the direction around the central axis O of the rotationaldriving shaft 300 inside the housing 8. The pump portions 3A to 3E areprovided in such a manner that the number of pump portions positioned onthe vertically lower side is larger than the number of pump portionspositioned on the vertically upper side with respect to the central axisO of the rotational driving shaft 300 with the housing 8 mounted on thevehicle.

Therefore, the present embodiment can further effectively reduce thevibration of the second unit 1B.

(2) The pump portions 3A to 3E (the plurality of plunger pumps) overlapone another in the axial direction of the rotational driving shaft 300.

Therefore, the present embodiment can prevent or cut down the increasein the number of parts of the second unit 1B, thereby achieving thereduction in the size of the second unit 1B.

(3) The pump portions 3A to 3E (the plurality of plunger pumps) eachinclude the central axis 360 extending radially around the central axisO of the rotational driving shaft 300, and the straight line defined byextending the central axis 360 of the arbitrary pump portion 3A or thelike beyond the central axis O of the rotational driving shaft 300 hasthe angle larger than zero degree in the direction around the centralaxis O of the rotational driving shaft 300 relative to the central axis360 of another pump portion 3C, 3D, or the like.

Therefore, the present embodiment can reduce the pulse pressure.

(4) The pump portions 3A to 3E (the plurality of plunger pumps) includethe two pump portions positioned on the vertically upper side and thethree pump portions positioned on the vertically lower side with respectto the central axis O of the rotational driving shaft 300 with thehousing 8 mounted on the vehicle.

Therefore, the present embodiment can improve the effect of reducing thepulse pressure while securing the discharge amount.

(5) The housing 8 includes the front surface 801 to which the motor 20coupled with the rotational driving shaft 300 is attached, the backsurface 802 opposite from the front surface 801, the bottom surface 803connected to the front surface 801 and the back surface 802 andpositioned on the vertically lower side with respect to the central axisO of the rotational driving shaft 300 with the housing 8 mounted on thevehicle, and the top surface 804 opposite from the bottom surface 803.At least one pump portion 3A of the three pump portions 3A, 3B, and 3Epositioned on the vertically lower side is disposed from the bottomsurface 803 into the housing 8.

Therefore, the present embodiment facilitates disposing the pumpportions 3A, 3B, and 3E at the generally even intervals in the directionaround the central axis O on the vertically lower side.

(6) The housing 8 includes the left side surface 805 (a first sidesurface) connected to the front surface 801, the back surface 802, thebottom surface 803, and the top surface 804, the right side surface 806(a second side surface) opposite from the left side surface 805, thefirst recessed portion 80A opened on the front surface 801, the topsurface 804, and the left side surface 805, and the second recessedportion 80B opened on the front surface 801, the top surface 804, andthe right side surface 806. The pump portions 3C and 3D, which are theone and the other of the two pump portions 3C and 3D positioned on thevertically upper side, are disposed from the first recessed portion 80Aand the second recessed portion 80B into the housing 8, respectively.

Therefore, the present embodiment facilitates disposing the pumpportions 3A to 3E at the generally even intervals in the directionaround the central axis O.

(7) The three pump portions 3A, 3B, and 3E positioned on the verticallylower side are disposed from the bottom surface 803, the left sidesurface 805 (the first side surface), and the right side surface 806(the second side surface) into the housing 8, respectively.

Therefore, the present embodiment facilitates disposing the pumpportions 3A, 3B, and 3E at the generally even intervals in the directionaround the central axis O on the vertically lower side.

(12) The second unit 1B (a hydraulic control apparatus) includes thehousing 8 including the fluid passages 11 and the like and therotational driving shaft 300 (a rotational shaft) provided therein, thefront surface 801 (a first surface), the back surface 802 (a secondsurface) opposite from the front surface 801, the bottom surface 803 (athird surface) connected to the front surface 801 and the back surface802, the top surface 804 (a fourth surface) opposite from the bottomsurface 803, the left side surface 805 (a fifth surface) connected tothe front surface 801, the back surface 802, the bottom surface 803, andthe top surface 804, the right side surface 806 (a sixth surface)opposite from the left side surface 805, the first recessed portion 80Aopened on the front surface 801, the top surface 804, and the left sidesurface 805, and the second recessed portion 80B opened on the frontsurface 801, the top surface 804, and the right side surface 806. Thehousing 8 is configured in such a manner that the motor coupled with therotational driving shaft 300 is attached to the front surface 801, andthe bottom surface 803 is positioned on the vertically lower side withrespect to the central axis O of the rotational driving shaft 300 andthe first recessed portion 80A and the second recessed portion 80B arepositioned on the vertically upper side with respect to the central axisO of the rotational driving shaft 300 with the housing 8 mounted on thevehicle. The second unit 1B further includes the pump portion 3A (afirst plunger pump) disposed from the bottom surface 803 into thehousing 8 and configured to be activated by the rotation of therotational driving shaft 300, the pump portion 3B (a second plungerpump) disposed from the portion of the left side surface 805 that ispositioned on the vertically lower side with respect to the central axisO of the rotational driving shaft 300 with the housing 8 mounted on thevehicle into the housing 8, and configured to be activated by therotation of the rotational driving shaft 300, the pump portion 3C (athird plunger pump) disposed from the first recessed portion 80A intothe housing 8 and configured to be activated by the rotation of therotational driving shaft 300, the pump portion 3D (a fourth plungerpump) disposed from the second recessed portion 80B into the housing 8and configured to be activated by the rotation of the rotational drivingshaft 300, and the pump portion 3E (a fifth plunger pump) disposed fromthe portion of the right side surface 806 that is positioned on thevertically lower side with respect to the central axis O of therotational driving shaft 300 with the housing 8 mounted on the vehicleinto the housing 8, and configured to be activated by the rotation ofthe rotational driving shaft 300.

Therefore, the present embodiment can further effectively reduce thevibration of the second unit 1B. Further, the present embodiment canimprove the effect of reducing the pulse pressure while securing thedischarge amount. Further, the present embodiment facilitates disposingthe pump portions 3A to 3E at the generally even intervals in thedirection around the central axis O.

(13) The pump portions 3A to 3E (the first to fifth plunger pumps)overlap one another in the axial direction of the rotational drivingshaft 300.

Therefore, the present embodiment can prevent or cut down the increasein the number of parts of the second unit 1B, thereby achieving thereduction in the size of the second unit 1B.

(14) The pump portions 3A to 3E (the first to fifth plunger pumps) eachinclude the central axis 360 extending radially around the central axisO of the rotational driving shaft 300, and the straight line defined byextending the central axis 360 of the arbitrary pump portion 3A or thelike beyond the central axis O of the rotational driving shaft 300 hasthe angle larger than zero degree in the direction around the centralaxis O of the rotational driving shaft 300 relative to the central axis360 of another pump portion 3C, 3D, or the like.

Therefore, the present embodiment can reduce the pulse pressure.

(15) The brake system 1 includes the first unit 1A including the strokesimulator 6 configured to generate the reaction force of the brakeoperation performed by the driver, and the second unit 1B including thehousing 8 including the fluid passages 11 and the like formed therein,the rotational driving shaft 300 provided inside the housing 8, and theplurality of pump portions 3A to 3E (plunger pumps) configured to beactivated by the rotation of the rotational driving shaft 300 anddisposed in the direction around the central axis O of the rotationaldriving shaft 300 inside the housing 8. The pump portions 3A to 3E areprovided in such a manner that the number of pump portions positioned onthe vertically lower side is larger than the number of pump portionspositioned on the vertically upper side with respect to the central axisO of the rotational driving shaft 300 with the housing 8 mounted on thevehicle.

Therefore, the present embodiment can further effectively reduce thevibration of the second unit 1B in the brake system 1 in which the firstunit 1A includes the stroke simulator 6.

Second Embodiment

First, a configuration will be described. In the following description,a configuration shared with the first embodiment will be identified bythe same reference numeral and a description thereof will be omitted.FIG. 13 is a perspective view similar to FIG. 8 that illustrates thesecond unit 1B according to the present embodiment with the pin PIN andthe like attached thereto. FIG. 14 is a perspective view similar to FIG.9 that illustrates the second unit 1B according to the presentembodiment in the state installed on the mount 100. FIG. 15 is a frontview similar to FIG. 10 that illustrates the second unit 1B according tothe present embodiment in the state installed on the mount 100. Nostructure for supporting the housing 8 (the front surface 801) isprovided on the X-axis positive direction side of the second mountportion 102. The mount 100 includes a third mount portion 103 providedintegrally with the first mount portion 101 and the like. The thirdmount portion 103 is disposed generally in parallel with the Y axis andthe Z axis. The third mount portion 103 extends from the end of thefirst mount portion 101 in the X-axis positive direction to the Z-axispositive direction side. A recessed portion 103 a opened on the Z-axispositive direction side is formed at an end of the third mount portion103 in the Z-axis positive direction. The bolt B2 is inserted in therecessed portion 103 a. A Y-axis negative direction side of the thirdmount portion 103 includes a recessed portion 103 b curved toward theY-axis positive direction side. The bolt B2 of the third mount portion103 is inserted and fixed in the bolt hole 858C of the housing 8. Thebolt B2 fixes the right side surface 806 of the housing 8 to the thirdmount portion 103 via the insulator 108. The hole 858C functions as thefixation portion for fixing the housing 8 to the vehicle body side (themount 100). The bolt B2, the collar member 106, and the washer 107 arethe structure supporting the housing 8 (the right side surface 806), andfunction as the support portion of the right side surface 806. The otherstructure of the support portion on the third mount portion 103 issimilar to the support portion on the second mount portion 102. Theother configuration is similar to the first embodiment.

FIG. 16 is an exploded perspective view illustrating a process forattaching the second unit 1B onto the mount 100. In a first process, theinsulator 108 and the collar member 106 are attached to the third mountportion 13. In a third process, the collar member 106 is sandwichedbetween the head portion (the washer 107) and the right side surface 806and fixed to the right side surface 806 due to the axial force of thebolt B2. Other processes are similar to the first embodiment.

Next, functions and effects will be described. The hole 858C for thefixation to the mount 100 is provided on the right side surface 806 ofthe housing 8. Therefore, the present embodiment can efficiently utilizethe side surface 806 of the housing 8 for the fixation to the mount 100while avoiding the interference with the connector portion 903. The hole858C extends horizontally, and the bolt B2 fixed in the hole 858C alsoextends horizontally. The support portion of the bottom surface 803, thesupport portion of the front surface 801, and the support portion of theright side surface 806 support the housing 8 in different directionsfrom one another, whereby the present embodiment can improve supportstrength against the load that can be applied to the housing 8 inmultiple directions. Further, the present embodiment can improve theeffect of preventing or reducing the vibration against the vibrationthat can occur in the housing 8 in multiple directions. Further, thehousing 8 is supported at the plurality of positions some distance awayfrom one another in the direction around the central axis O, whereby thepresent embodiment effectively prevents or reduces the vibration of thesecond unit 1B in the direction around the central axis O. The holes858A and 858B, and the hole 858C are disposed on both the opposite sidesof the central axis O from each other in the Z-axis direction.Therefore, the present embodiment can further effectively reduce thevibration around the central axis O of the second unit 1B by supportingthe housing 8 on the opposite sides of the central axis O from eachother in the Z-axis direction. The center of gravity of the second unit1B is positioned between the support portion of the right side surface806 (the portion where the right side surface 806 is attached to thethird mount portion 103) and the support portion of the bottom surface803 (the portion where bottom surface 803 is attached to the first mountportion 101) in the Z-axis direction. The present embodiment can improvethe strength of supporting the second unit 1B by supporting the secondunit 1B on the opposite sides of the center of gravity from each otherin the Z-axis direction. A straight line connecting the support portionand the support portion of the housing 8 becomes an axis when thehousing 8 swings. A reduction in a distance between this axis and thebehavior sensor leads to a reduction in an amplitude of the swing of thebehavior sensor when the housing 8 vibrates, thereby contributing topreventing or reducing the deterioration of the detection accuracy ofthe behavior sensor. A straight line connecting the support portion ofthe right side surface 806 and the support portion of the bottom surface803 becomes one of the above-described axes when the housing 8 swings.The hole 858C is provided on the vertically upper side of the right sidesurface 806. Therefore, the present embodiment facilitates disposing theabove-described axis close to the behavior sensor. The backpressure port874 is not covered by the third mount portion 103 due to the provisionof the recessed portion 103 b on the third mount portion 103, whichfacilitates the work of attaching the pipe 10X to the right side surface806. Other functions and effects are similar to the first embodiment.

Other Embodiments

Having described the embodiments for implementing the present inventionwith reference to the drawings, the specific configuration of thepresent invention is not limited to the embodiments, and the presentinvention also includes a design modification and the like thereof madewithin a range that does not depart from the spirit of the presentinvention.

In the following description, technical ideas recognizable from theembodiments will be listed.

(8) The hydraulic control apparatus described in the above-describeditem (6) further includes the control unit configured to contribute tothe driving of the motor. The part of the bolt for attaching the controlunit to the back surface protrudes in each of the first recessed portionand the second recessed portion.(9) In the hydraulic control apparatus described in the above-describeditem (5), the housing includes the first fluid pool portion connected tothe intake portion of each of the plurality of plunger pumps. The firstfluid pool portion is disposed from the top surface into the housing,and is located between the two plunger pumps positioned on thevertically upper side in the direction around the central axis of therotational driving shaft.(10) In the hydraulic control apparatus described in the above-describeditem (5), the housing includes the second fluid pool portion configuredto store therein the fluid leaking from the plurality of plunger pumps.The second fluid pool portion is disposed from the bottom surface intothe housing.(11) In the hydraulic control apparatus described in the above-describeditem (2), the plurality of plunger pumps is disposed at the generallyeven intervals in the direction around the central axis of therotational driving shaft.(16) In the hydraulic control apparatus described in the above-describeditem (15), the plurality of plunger pumps overlaps each other or oneanother in the axial direction of the rotational driving shaft.(17) In the hydraulic control apparatus described in the above-describeditem (16), the plurality of plunger pumps each includes the central axisextending radially around the central axis of the rotational drivingshaft, and the straight line defined by extending the central axis ofarbitrary one of the plunger pumps beyond the central axis of therotational driving shaft has the angle larger than zero degree in thedirection around the central axis of the rotational driving shaftrelative to the central axis of another one of the plunger pumps.

Having described merely several embodiments of the present invention,those skilled in the art will be able to easily appreciate that theembodiments described as the examples can be modified or improved invarious manners without substantially departing from the novel teachingsand advantages of the present invention. Therefore, such modified orimproved embodiments are intended to be also contained in the technicalscope of the present invention. The above-described embodiments may alsobe arbitrarily combined.

The present application claims priority under the Paris Convention toJapanese Patent Application No. 2015-194418 filed on Sep. 30, 2015. Theentire disclosure of Japanese Patent Application No. 2015-194418 filedon Sep. 30, 2015 including the specification, the claims, the drawings,and the abstract is incorporated herein by reference in its entirety.

REFERENCE SIGN LIST

-   1 brake system-   1A first unit-   1B second unit (hydraulic control apparatus)-   11 supply fluid passage (fluid passage)-   20 motor-   3A pump portion (first plunger pump)-   3B pump portion (second plunger pump)-   3C pump portion (third plunger pump)-   3D pump portion (fourth plunger pump)-   3E pump portion (fifth plunger pump)-   300 rotational driving shaft-   360 central axis-   8 housing-   801 front surface (first surface)-   802 back surface (second surface)-   803 bottom surface (third surface)-   804 top surface (fourth surface)-   805 left side surface (fifth surface, first side surface)-   806 right side surface (sixth surface, second side surface)-   80A first recessed portion-   80B second recessed portion

1. A hydraulic control apparatus comprising: a housing including a fluidpassage provided therein and configured to be mounted on a vehicle; arotational driving shaft provided inside the housing; and a plurality ofplunger pumps configured to be activated by a rotation of the rotationaldriving shaft and disposed in a direction around a central axis of therotational driving shaft inside the housing, the plunger pumps beingprovided in such a manner that the number of plunger pumps positioned ona vertically lower side is larger than the number of plunger pumpspositioned on a vertically upper side with respect to the central axisof the rotational driving shaft with the housing mounted on the vehicle.2. The hydraulic control apparatus according to claim 1, wherein theplurality of plunger pumps overlaps each other or one another in anaxial direction of the rotational driving shaft.
 3. The hydrauliccontrol apparatus according to claim 2, wherein the plurality of plungerpumps each includes a central axis extending radially around the centralaxis of the rotational driving shaft, and a straight line defined byextending the central axis of arbitrary one of the plunger pumps beyondthe central axis of the rotational driving shaft has an angle largerthan zero degree in the direction around the central axis of therotational driving shaft relative to the central axis of another one ofthe plunger pumps.
 4. The hydraulic control apparatus according to claim3, wherein the plurality of plunger pumps includes two plunger pumpspositioned on the vertically upper side and three plunger pumpspositioned on the vertically lower side with respect to the central axisof the rotational driving shaft with the housing mounted on the vehicle.5. The hydraulic control apparatus according to claim 4, wherein thehousing includes a front surface to which a motor coupled with therotational driving shaft is attached, a back surface opposite from thefront surface, a bottom surface connected to the front surface and theback surface and positioned on the vertically lower side with respect tothe central axis of the rotational driving shaft with the housingmounted on the vehicle, and a top surface opposite from the bottomsurface, and wherein at least one of the three plunger pumps positionedon the vertically lower side is disposed from the bottom surface intothe housing.
 6. The hydraulic control apparatus according to claim 5,wherein the housing includes a first side surface connected to the frontsurface, the back surface, the bottom surface, and the top surface, asecond side surface opposite from the first side surface, a firstrecessed portion opened on the front surface, the top surface, and thefirst side surface, and a second recessed portion opened on the frontsurface, the top surface, and the second side surface, and wherein oneand the other of the two plunger pumps positioned on the verticallyupper side are disposed from the first recessed portion and the secondrecessed portion into the housing, respectively.
 7. The hydrauliccontrol apparatus according to claim 6, wherein the three plunger pumpspositioned on the vertically lower side are disposed from the bottomsurface, the first side surface, and the second side surface into thehousing, respectively.
 8. The hydraulic control apparatus according toclaim 6, further comprising a control unit configured to contribute todriving of the motor, wherein a part of a bolt for attaching the controlunit to the back surface protrudes in each of the first recessed portionand the second recessed portion.
 9. The hydraulic control apparatusaccording to claim 5, wherein the housing includes a first fluid poolportion connected to an intake portion of each of the plurality ofplunger pumps, and wherein the first fluid pool portion is disposed fromthe top surface into the housing, and is located between the two plungerpumps positioned on the vertically upper side in the direction aroundthe central axis of the rotational driving shaft.
 10. The hydrauliccontrol apparatus according to claim 5, wherein the housing includes asecond fluid pool portion configured to store therein fluid leaking fromthe plurality of plunger pumps, and wherein the second fluid poolportion is disposed from the bottom surface into the housing.
 11. Thehydraulic control apparatus according to claim 2, wherein the pluralityof plunger pumps is disposed at generally even intervals in thedirection around the central axis of the rotational driving shaft.
 12. Ahydraulic control apparatus comprising: a housing, the housing includinga fluid passage and a rotational shaft provided therein, a firstsurface, a second surface opposite from the first surface, a thirdsurface connected to the first surface and the second surface, a fourthsurface opposite from the third surface, a fifth surface connected tothe first, second, third, and fourth surfaces, a sixth surface oppositefrom the fifth surface, a first recessed portion opened on the first,fourth, and fifth surfaces, and a second recessed portion opened on thefirst, fourth, and sixth surfaces, the housing being configured in sucha manner that a motor coupled with the rotational shaft is attached tothe first surface, and the third surface is positioned on a verticallylower side with respect to a central axis of the rotational shaft andthe first recessed portion and the second recessed portion arepositioned on a vertically upper side with respect to the central axisof the rotational shaft with the housing mounted on a vehicle; a firstplunger pump disposed from the third surface into the housing andconfigured to be activated by a rotation of the rotational shaft; asecond plunger pump disposed from a portion of the fifth surface that ispositioned on the vertically lower side with respect to the central axisof the rotational shaft with the housing mounted on the vehicle into thehousing, the second plunger pump being configured to be activated by therotation of the rotational shaft; a third plunger pump disposed from thefirst recessed portion into the housing and configured to be activatedby the rotation of the rotational shaft; a fourth plunger pump disposedfrom the second recessed portion into the housing and configured to beactivated by the rotation of the rotational shaft; and a fifth plungerpump disposed from a portion of the sixth surface that is positioned onthe vertically lower side with respect to the central axis of therotational shaft with the housing mounted on the vehicle into thehousing, the fifth plunger pump being configured to be activated by therotation of the rotational shaft.
 13. The hydraulic control apparatusaccording to claim 12, wherein the first to fifth plunger pumps overlapone another in an axial direction of the rotational shaft.
 14. Thehydraulic control apparatus according to claim 13, wherein the first tofifth plunger pumps each include a central axis extending radiallyaround the central axis of the rotational shaft, and a straight linedefined by extending the central axis of arbitrary one of the plungerpumps beyond the central axis of the rotational shaft has an anglelarger than zero degree in the direction around the central axis of therotational shaft relative to the central axis of another one of theplunger pumps.
 15. A brake system comprising: a first unit including astroke simulator configured to generate a reaction force of a brakeoperation performed by a driver; and a second unit including a housingincluding a fluid passage formed therein, a rotational driving shaftprovided inside the housing, and a plurality of plunger pumps configuredto be activated by a rotation of the rotational driving shaft anddisposed in a direction around a central axis of the rotational drivingshaft inside the housing, the plunger pumps being provided in such amanner that the number of plunger pumps positioned on a vertically lowerside is larger than the number of plunger pumps positioned on avertically upper side with respect to the central axis of the rotationaldriving shaft with the housing mounted on the vehicle.
 16. The hydrauliccontrol apparatus according to claim 15, wherein the plurality ofplunger pumps overlaps each other or one another in an axial directionof the rotational driving shaft.
 17. The hydraulic control apparatusaccording to claim 16, wherein the plurality of plunger pumps eachincludes a central axis extending radially around the central axis ofthe rotational driving shaft, and a straight line defined by extendingthe central axis of arbitrary one of the plunger pumps beyond thecentral axis of the rotational driving shaft has an angle larger thanzero degree in the direction around the central axis of the rotationaldriving shaft relative to the central axis of another one of the plungerpumps.